jriske wrote: … I'll take ANY ideas
Well, since you said ANY ideas--- get a Mac. Mac Photos has Smart Albums, so I have one that uses the requirement: Album is not any.
Some use an iCloud Shared Photo Library as a trick to separate pictures into two groups:
See: How to use iCloud Shared Photo Library – Apple Support (UK)
You can share the "shared Library" only with yourself.
Another option is to mark all the ones that are in Albums. Then put ALL the pictures in a NotMarked album, select the marked ones, and delete those from the NotMarked album. Then work on the rest.
The only simple mark available is the little heart for Favorite. So you could select all for each album, tap the heart, and continue to the next. Then you just look for pictures with no heart. (I've seen some movies recently that I would describe as "pictures with no heart.") This might encourage you to keep albums that have only favorites, so you don't go looking at fuzzy pictures, or 7 shots of the same thing.