Photos should not be crashing, even if the library has problems. You may want to report the bug to Apple.
I noticed after the Catalina upgrade that the albums have been very slow to sync. It took days, before the photos appeared in them. Are you seeing the same empty albums on your iCloud web page at www.icloud.com?
I would not delete albums, while the syncing with iCloud has not yet finished. Wait until the staus bar below the Photos view is showing "Updated just now".
Does your extenal SSD have the correct file system format (APFS or MacOS Extended (Journaled), and not case-sensitive)?