Without any doubt, AVIF is a must nowadays.
There must be some major difficulties in implementing this, otherwise there is no reason not to support it right now.

######## PART 1/3 ########

The problem with AVIF:
- PHP image manipulation is handled by two different software component (GD, ImageMagick) that use different libraries to support AVIF format (libavif, libde265, libheif)
- some "old" distros that Plesk still need to support, don't have those libraries available from their package manager, thus there is the need to manually compile them (with required dependencies)
- Plesk official AVIF support obviously need to be implemented for every Plesk supported platform and for all PHP supported versions and variant (fastcgi, fpm)

After all the time passed from the initial request and initial AVIF PHP support (PHP 8.1 was released on November 2021) and despite the commercial product nature of Plesk software, it seems that the above task is still very complex.

That said, I've managed to implement AVIF support for both GD and ImageMagick in a special case:
- AlmaLinux 9.x (but it should work in similar RedHat based distros)
- PHP 8.1.x, PHP 8.2.x, PHP 8.3.x (PHP8.4.x actually fail with imagick extension compile)
- no IMAP PHP module support
- only fastgci PHP mode (fpm mode need some extra works that actually exceeds my knowledge)

DISCLAIMERS:
I've tried to make the installation completely separated from the rest of the system with only minimal integration.
However, since I'm not an experienced Linux software developer/builder/maintainer use the following procedure at your own risk!

Let's start with instructions for:
- PHP 8.3.14
- ImageMagick 7.1.1-41

######## PART 2/3 ########

Install epel repository
# sudo dnf install epel-release
# sudo dnf update

Install compiler tools
# sudo dnf install gcc g++ cmake autoconf wget

Install PHP dependencies
# sudo dnf install libxml2-devel sqlite-devel krb5-devel openssl-devel bzip2-devel libcurl-devel libdb-devel enchant-devel libpng-devel libwebp-devel libjpeg-devel libXpm-devel freetype-devel gmp-devel openldap-devel oniguruma-devel unixODBC-devel postgresql-server-devel aspell-devel libedit-devel net-snmp-devel libtidy-devel libxslt-devel libzip-devel

Install AVIF support for PHP GD
# sudo dnf install libavif-devel

Download PHP source
# wget https://www.php.net/distributions/php-8.3.14.tar.gz
# tar xzvf php-8.3.14.tar.gz
# cd php-8.3.14

Configure PHP build (based on options used in official Plesk builds)
Note 1: we use a custom base path /opt/customphp/8.3/
Note 2: we not enable IMAP support because it require to download it's own source code
Note 2: we add --with-avif for GD

./configure '--bindir=/opt/customphp/8.3/bin' '--runstatedir=/run' '--localedir=/opt/customphp/8.3/share/locale' '--localstatedir=/opt/customphp/8.3/var' '--libdir=/opt/customphp/8.3/lib64' '--docdir=/opt/customphp/8.3/share/doc' '--prefix=/opt/customphp/8.3' '--mandir=/opt/customphp/8.3/share/man' '--datadir=/opt/customphp/8.3/share' '--sbindir=/opt/customphp/8.3/sbin' '--exec-prefix=/opt/customphp/8.3' '--sysconfdir=/opt/customphp/8.3/etc' '--sharedstatedir=/opt/customphp/8.3/com' '--includedir=/opt/customphp/8.3/include' '--libexecdir=/opt/customphp/8.3/lib64' '--infodir=/opt/customphp/8.3/share/info' '--build=x86_64-redhat-linux-gnu' '--host=x86_64-redhat-linux-gnu' '--disable-debug' '--disable-gcc-global-regs' '--disable-rpath' '--enable-calendar' '--enable-exif' '--enable-ftp' '--enable-litespeed' '--enable-phpdbg' '--enable-re2c-cgoto' '--enable-sockets' '--enable-sysvmsg' '--enable-sysvsem' '--enable-sysvshm' '--enable-xml' '--with-bz2' '--with-config-file-path=/opt/customphp/8.3/etc' '--with-config-file-scan-dir=/opt/customphp/8.3/etc/php.d' '--with-enchant=shared' '--with-gettext' '--with-gmp' '--with-iconv' '--with-kerberos' '--with-layout=GNU' '--with-libdir=lib64' '--with-libxml' '--with-openssl' '--with-pic' '--with-system-tzdata' '--with-zlib' '--without-gdbm' '--without-pear' '--enable-bcmath=shared' '--enable-dba=shared' '--enable-dom=shared' '--enable-fileinfo=shared' '--enable-gd=shared' '--with-webp' '--enable-intl=shared' '--enable-mbregex' '--enable-mbstring=shared' '--enable-mysqlnd=shared' '--enable-pcntl' '--enable-pdo=shared' '--enable-phar=shared' '--enable-posix=shared' '--enable-soap=shared' '--enable-sysvmsg=shared' '--enable-sysvsem=shared' '--enable-sysvshm=shared' '--enable-xmlreader=shared' '--enable-xmlwriter=shared' '--with-curl=shared' '--with-db4=/usr' '--with-freetype' '--with-jpeg' '--with-ldap=shared' '--with-ldap-sasl' '--with-libedit' '--with-mysql-sock=/var/lib/mysql/mysql.sock' '--with-mysqli=shared,mysqlnd' '--with-pdo-mysql=shared,mysqlnd' '--with-pdo-odbc=shared,unixODBC,/usr' '--with-pdo-pgsql=shared,/usr' '--with-pdo-sqlite=shared' '--with-pgsql=shared' '--with-pspell=shared' '--with-snmp=shared,/usr' '--with-sqlite3=shared' '--with-tidy=shared,/usr' '--with-unixODBC=shared,/usr' '--with-xpm' '--with-xsl=shared' '--with-zip=shared' '--without-readline' '--with-avif' 'build_alias=x86_64-redhat-linux-gnu' 'host_alias=x86_64-redhat-linux-gnu' 'CFLAGS=-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fstack-protector-strong -m64 -march=x86-64-v2 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fno-strict-aliasing -pipe -Wno-unused-function' 'CPPFLAGS=' 'CXXFLAGS=-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fstack-protector-strong -m64 -march=x86-64-v2 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection'

Build PHP
# make

Install PHP
# sudo make install

Copy php.ini file from Plesk
# mkdir /opt/customphp/8.3/etc/
# cp /opt/plesk/php/8.3/etc/php.ini /opt/customphp/8.3/etc/

Exit from PHP source code directory
# cd ..

Up to this point, only PHP GD has AVIF support.

######## PART 3/3 ########

Let's add ImageMagick with AVIF
# sudo dnf install libheif-devel

Bonus (ImageMagick can also support JpegXL)
# sudo dnf install libjxl-devel

Download latest source code (actually 7.1.1-41)
# wget https://www.imagemagick.org/download/ImageMagick.tar.gz
# tar xzvf ImageMagick.tar.gz
# cd ImageMagick-7.1.1-41

Configure the build to use the same custom PHP path
# ./configure --prefix=/opt/customphp/8.3

Make and install
# make
# sudo make install

Check ImageMagick AVIF support
# /opt/customphp/8.3/bin/convert -list format | grep AVIF
AVIF rw+ AV1 Image File Format (1.16.1)

CHECK ImageMagick JPEG XL support
# /opt/customphp/8.3/bin/convert -list format | grep JXL
JXL* rw+ JPEG XL (ISO/IEC 18181) (libjxl 0.7.0)

Exit from ImageMagick source code directory
# cd ..

Install PHP imagick module
# wget https://pear.php.net/go-pear.phar
# /opt/customphp/8.3/bin/php go-pear.phar
(specify path /opt/customphp/8.3 if asked)

Install imagick module
# PKG_CONFIG_PATH=/opt/customphp/8.3/lib/pkgconfig; sudo /opt/customphp/8.3/bin/pecl install imagick
(specify path /opt/customphp/8.3 if asked)

As final step let's inform Plesk about the new custom PHP build

Copy all extension.ini files from Plesk equivalent version of PHP (thus you'll be able to enable/disable extensions from the plesk GUI)
# sudo cp -rf /opt/plesk/php/8.3/etc/php.d /opt/customphp/8.3/etc/
Remove IMAP initialization file (because we've not compiled it in custom PHP)
# sudo rm /opt/customphp/8.3/etc/php.d/imap.ini

Add the custom PHP fastcgi handler to Plesk
# sudo plesk bin php_handler --add -displayname 8.3.14-custom -path /opt/customphp/8.3/bin/php-cgi -phpini /opt/customphp/8.3/etc/php.ini -type fastcgi -id 8.3.14-fastcgi-custom -clipath /opt/customphp/8.3/bin/php

(If you'll need to remove the handler just do: #sudo plesk bin php_handler --remove -id 8.3.14-fastcgi-custom )

Update Plesk GUI
# sudo plesk bin php_handler --reread
# sudo plesk sbin packagemng -sdf

Now you can go to Domains -> {a_domain_name} -> PHP and choose the PHP version 8.3.14-custom as FastCGI application served by Apache.
Click the side link "View the phpinfo() page" and search for AVIF.
You should see:
GD -> AVIF Support : enabled
imagick -> ImageMagick supported formats -> ... AVIF ... JXL ...

You really need to consider adding support for Avif, it performs better than Webp, and even Google is supporting it: https://developers.google.com/search/blog/2024/08/happy-avifriday

Please Plesk!

Plesk must be dead asked for it 2 years ago... and still nothing???

Please add it

The performance for websites is huge with this upgrade. Please support the image type in Plesk :)

this is mandatory now ... also google suggests using it.

No puedo entender como a estas alturas seguimos sin sin soporte para AVIF

Tengo urgencia ya que estoy implementando un proyecto nuevo en WordPress y me piden tener habilitada esta opción. Elegí trabajar con un VPS de Axarnet y desde mi desconocimiento de Plesk, ya que venía de hosting con cPanel, creí que esto ya venía habilitado. ME gustaría saber para cuando tendrán implementado esta actualización. Muchas gracias.

Any news on this?

Please add AVIF support to Plesk

Please add AVIF support to Plesk - would be very helpful for WordPress, which now supports AVIF format.

Please add the AVIF support, it is well supported now

Please add the AVIF support, it is well supported now

WordPress now support the AVIF format. Please include AVIF support in the next update.

Microsoft Edge will soon be released with AVIF support, then all browsers will be able to do this.
Please turn on avif support by default now.

Would be great to get the support in a timely manner so you can work with it. I am already receiving the first complaints. Most major browsers already support the format.

All CMS we work with support AVIF, but not Plesk.
Please AVIF support with the next update.