So i updated my version of php to the new version (8.0). And everything works fine, except for my adminer.
It's caused by my version of adminer being out of date because php8.0 doesn't have the function magic_quotes.
And the only command i have find to get adminer is this one: sudo apt-get install adminer
But it doesn't work...
Support was added in December 2020, unfortunately only weeks after your question @The-Evil-Fox. The only problem is it seems the Ubuntu repo is not up to date so if you install via apt install adminer you'll still be on a version that doesn't support PHP 8.
The easiest way I found to update is to still install it that way, but then use wget to download the latest version of adminer.php. So do something like this:
cd /usr/share/adminer
sudo wget https://www.adminer.org/latest.php
sudo mv latest.php adminer.php
Done! That worked for me anyway... I'm not a Ubuntu pro though, so no idea why repo is so out of date.