I used to use DupeGuru which has some photo-specific dupe detection where you can fuzzy match image dupes based on content: https://dupeguru.voltaicideas.net/
But I switched over to czkawka, which has a better interface for comparing files, and seems to be a bit faster: https://github.com/qarmin/czkawka
Unfortunately, neither of these are integrated into Photoprism, so you still have to do some file management outside the database before importing.
I also haven't used Photoprism extensively yet (I think it's running on one of my boxes, but I haven't gotten around to setting it up), but I did find that it wasn't really built for file-based libraries. It's a little more heavyweight, but my research shows that Nextcloud Memories might be a better choice for me (it's not the first-party Nextcloud photos app, but another one put together by the community): https://apps.nextcloud.com/apps/memories
But I switched over to czkawka, which has a better interface for comparing files, and seems to be a bit faster: https://github.com/qarmin/czkawka
Unfortunately, neither of these are integrated into Photoprism, so you still have to do some file management outside the database before importing.
I also haven't used Photoprism extensively yet (I think it's running on one of my boxes, but I haven't gotten around to setting it up), but I did find that it wasn't really built for file-based libraries. It's a little more heavyweight, but my research shows that Nextcloud Memories might be a better choice for me (it's not the first-party Nextcloud photos app, but another one put together by the community): https://apps.nextcloud.com/apps/memories