I recently had a site that I did not use or update regularly have the admin dashboard corrupted.
There was no styling, only text jumbled up on the screen.
It was impossible to navigate.
I tried to clear the cache, disable the plugins folder via file manager/ftp but it did not work.
I found this code to add to the wp-config.php file after WP_DEBUG line near the bottom
Add this and save and it should do the trick.
The other option is to revert to PHP 8 or 7.4 if you are on 8.1 or 8.2.