Ran into this as well; I believe this is a unique intersection of PHP 8.0 with versions of Xdebug >= 3.3.0. Downgrading to 3.2.x worked, however PHP 8.0 is of course end of life. Running a supported version of PHP along with a current/supported version of Xdebug is likely to resolve this more definitively.

Read elsewhere this is potentially related to https://bugs.xdebug.org/view.php?id=2222 so this might still be an issue, but for sure this is a version mismatch issue with Xdebug and language features utilized in the entity proxy.