While you've figured this out, others will come (like myself) to see how you did this.
# perhaps you did the following to see what modules were present
> apache2ctl -M
# the result of the above command may have returned an error such as:
apache2:
Syntax error on line 146 of /etc/apache2/apache2.conf:
Syntax error on line 2 of /etc/apache2/mods-enabled/php8.0.load:
Cannot load /usr/lib/apache2/modules/libphp8.0.so into server:
/usr/lib/apache2/modules/libphp8.0.so:
cannot open shared object file: No such file or directory
Action '-M' failed.
# so you removed the problematic module that was no longer installed
# by doing the following (as appropriate given the error above)
> sudo a2dismod php8.0
# you needed to restart your server after that
> sudo systemctl restart apache2
# if you tested the server in a browser html should function...
# however you perhaps desired the use of another php module
# and added another one (8.1) that is install by default in Ubuntu 22.04
> sudo a2enmod php8.1
# you restarted apache again and it worked?
> sudo systemctl restart apache2
Perhaps you were using mod_userdir
and also needed to update the apache php module configuration file:
/etc/apache2/mods-enabled/php8.1.conf
By commenting out the following lines:
<IfModule mod_userdir.c>
<Directory /home/*/public_html>
php_admin_flag engine Off
</Directory>
</IfModule>
So that they looked like this:
#<IfModule mod_userdir.c>
# <Directory /home/*/public_html>
# php_admin_flag engine Off
# </Directory>
#</IfModule>
# finally you restarted apache2 again:
sudo systemctl restart apache2
# and everything was back to normal?
Did you do something like this?