My original problem was as follows:
Lightroom CC on Windows 10 would give me the 'local catalog damaged' prompt when starting the program.
Lightroom CC crashes immediatly after clicking 'ok'
Lightroom CC therefore can't connect to the cloud to repair catalog
What fixed it for me:
Going into the Data folder
Deleting 'profiles' folder
Going into the folder with long string of numbers/letters
Deleted all 'Managed Catalog' files
Deleted 'preview' folder and preview.db
restarting Lightroom CC for Desktop
Lightroom CC regenerated all of the deleted folders and files when started and didn't crash. I have access to all my photos including the ones which were uploaded via my iPhone. There appears to be no damage at all to any of my images (which makes sense because of the catalog being in the cloud)
I write this all down bc I was stuck without Lightroom CC since January 2021 and could not find anyone with a solution that worked for my specific issue. I hope this helps.