phpThumb snippet is not compatible with PHP 8.
phpThumb uses the curly brackets method, which deprecated as of PHP 7.4 and incompatible with PHP 8. Do not change you PHP version if you use phpThumb until it gets fixed.
I'm going to setup a demo and test for PHP 8.
Probably allot of plugins etc. also needs to be fixed.
I noticed an updated site to EVO 3 had some issues but don't know about a clean version.