Today I upgraded my NC instance from Ubuntu 18.04 to 20.04. I still have the issue, that I can’t switch to PHP 7.4.
For my Apache virtual server used for NC, I currently have the following handler set:
SetHandler "proxy:unix:/run/php/php7.2-fpm.nextcloud.sock|fcgi://localhost"
/etc/php/7.2/fpm/pool.d/nextcloud.conf the following is set

So far, so good, this is the configuration which is working, but would like to move to PHP 7.4.
I copied /etc/php/7.2/fpm/pool.d/nextcloud.conf to /etc/php/7.4/fpm/pool.d/nextcloud.conf and modified the “listen” entry to:
listen = /run/php/php"7.4"-fpm.nextcloud.sock
Restarted php7.4-fpm (systemctl restart php7.4-fpm.service).
Now, as soon as I change the SetHandler entry for the Apache virtual server for NC to
SetHandler "proxy:unix:/run/php/php7.4-fpm.nextcloud.sock|fcgi://localhost"
and restart Apache, I get the following:
The only I can get into my NC, is to revert back the Apache config to 7.2.
Would appreciate your help, am stuck.
Thx!


