If it’s phpmyadmin for a particular user, is there a php.ini file in /home/user/etc/php7.4 or some other per-user location?
There are a few php.ini settings that affect upload and post limits.
memory_limit
post_max_size
upload_max_filesize
file_uploads
max_file_uploads
It takes a lot of tweaking and restarts to get it right. Make sure to restart the correct php-fpm service when there’s more than one. Use a phpinfo() file to compare local and master columns after making changes.
There may also be MySQL limits to increase for PHP apps that connect to MySQL.