22.4.2 crashing since update to Big Sur, now won't open at all

Try trashing your Photoshop preferences. Press and hold Option+Command+Shift (Mac OS) immediately after launching Photoshop. You will be prompted to delete the current settings.

(Mac OS only) Open the Preferences folder in the Library folder, and drag the Adobe Photoshop CS Settings folder to the Trash.

This action only affects the items found in the preferences dialog box. Numerous program settings are stored in the Adobe Photoshop Preferences file, including general display options, file-saving options, performance options, cursor options, transparency options, type options, and options for plug‑ins and scratch disks. Brushes (and lots of other setting) are not affected by the above instructions for deleting preferences. You may wish to make a screen capture of the settings in the Preferences dialog to reset them prior to deleting of this file.

Also: https://helpx.adobe.com/photoshop/using/preferences.html

To manually delete Photoshop preferences:
Quit Photoshop.
Navigate to Photoshop's Preferences folder.
macOS: Users/[user name]/Library/Preferences/Adobe Photoshop [version] Settings
The user Library folder is hidden by default on macOS. To access files in the hidden user Library folder, see How to access hidden user library files.

Drag the entire Adobe Photoshop [Version] Settings folder to the desktop or somewhere safe for a back-up of your settings