First thing: how is your SSD drive formatted? To avoid damaging the Photos Library an external drive must be formatted in either APFS format or Mac OS Extended (Journaled) format. Additionally, the drive can not have had Time Machine on it since it was formatted. There have been so many problems with using incompatible drives that the newest macOSs won't even allow a Library on a non-Mac formatted drive to open, since there is a chance of damaging the Photos database. See this:
Move your Photos library to save space on your Mac - Apple Support
If this drive is in a an incompatible format, stop running Photos with it immediately! A Photos Library can sit on an incompatible drive, but running it may corrupt the database.
If your drive is properly formatted, then I'm not sure what's going on. I'm on 15.3, and I just did a search for "Red Dress." I got 28 hits with people in red dresses.
I did another search for "jeans," and I got 1300 hits. So the problem is not macOS15.
I'm not sure what "let it sit" means, but ideally you want Photos to know that scanning will not drain the battery or slow down your work. Scanning will be quickest if the computer is plugged in and left alone. Some would say to leave the mac on with Photos running in the background, which is what I would do.
Are you plugging and unplugging the SSD? That's a problem with a laptop. I would turn off iCloud before unplugging a drive is a Photos Library.
If your drive is formatted properly (APFS for an SSD) then try a Smart Album. When I did "Text is jeans" in a Smart Album, I also got 1300 hits.
If your drive is formatted properly, does face ID work?
Let us know…
