For the #homelab #NAS folks: is there a tool for helping me find duplicate/exact copies of files across directories? And maybe replace them with a symlink?

Copied over several laptop backups (plain files/dirs because that’s what I had in most cases on old external HDDs) and I can see I’ve got duplicated ebook files, video courses, and stuff like that that were on multiple machines before. I don’t need to store multiple copies and can’t go back to these (now nonexistent) machines and make better backups of some kind, so I wanted to modify what I have.