Photoshop not loading - stuck at splash screen [OSX Big Sur]

I am not a Mac user so my advice might not be 100% valid, but this will at least bump your thread back to thhe top of page one.  I'll also edit your subject line to shown you are using Big Sur as your issue might be OS specific.

The Splash Screen updates and shows the progress through the various checks that Photoshop does as it opens.  You can see mine was 'scanning for plugins' when I froze it to grab this screen shot, but it will also look at available fonts, alocated memory, scratch space as well as Preferences which it will use to load the last used workspace in its last used state.  If any of those are corrupted it can stop Photoshop loading.

Does your splash screen show any useful information at the time it stops loading?  That could show exactly where the issue is.

You can hold down the Shift key when starting Photoshop which will force it to ignore third party plugins.  If that fixes it, I think the only way to narrow it down to the problem plugin is to rename each plugin's folder one at a time in Finder,  This is just a guess, and not something I have ever tried.

This tool used to fix OSX font issues, but it is a few years old now

Troubleshoot fonts issues in Adobe Photoshop

You could try using the cleaner tool and reinstalling again

Use the Creative Cloud Cleaner tool to solve installation problems (adobe.com)

These should give you some things to try, and we'll hope some Mac experts happen along soon.