It depends which program you're using, for example even tar will preserve hard links. Or on the other side something like duplicacy will just deduplicate everything that has the same content.
Data Hoarder
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
deduplicating is fine, the question is what it will do on a restore.
As far as I can tell from searching the web, duplicacy will restore two (or more) hard linked files as separate files. (Apart from the obvious one of losing the connection, your restore directory takes more space than the original).
Restic (again searching, but this I can probably test since I use restic) will restore them properly -- i.e., preserving the hard link
Why wouldn't you do a small test and find out before throwing literally everything at it?