Thanks you, I followed your steps more or less and I think this way is simplier.
Worked on Nextcloud v22
Installing dependencies:
sudo apt-get install imagemagick-common php-imagick ffmpeg libmagickcore-dev libde265 libheif
Checking if worked, search for extensions
php -r 'phpinfo();' | grep HEIC
Add setup in config.php
sudo nano /var/www/nextcloud/config/config.php
'enable_previews' => true,
'preview_max_x' => 1000,
'preview_max_y' => 1000,
'enabledPreviewProviders' => [
'OC\Preview\TXT',
'OC\Preview\MarkDown',
'OC\Preview\PDF',
'OC\Preview\MSOfficeDoc',
'OC\Preview\JPEG',
'OC\Preview\PNG',
'OC\Preview\GIF',
'OC\Preview\BMP',
'OC\Preview\XBitmap',
'OC\Preview\MP3',
'OC\Preview\HEIC',
'OC\Preview\Movie',
'OC\Preview\MKV',
'OC\Preview\MP4',
'OC\Preview\AVI',
],
Restart webserver:
sudo systemctl restart apache2