One quick point about non-Apple Time Machine destinations. Another thing you can do if your storage or NAS isn’t fully TM compatible is create an HFS+ sparsebundle on the storage and point Time Machine to that. An HFS+ sparsebundle supports all the symlinks, permissions, and attributes that Time Machine needs.
Time Machine is my primary backup, and likely always will be. It’s easy – you can effortlessly scroll through the versioning for individual files.
More importantly, is that for “Apple’s” apps, Time Machine elevates from a simple file based backup and is integrated into the UI. Recovering a deleted Photos photo (or Aperture photo RIP) from a file based backup is a pain. But with Time Machine, it just pops right back into place and Time Machine / Photos handles the database edits required.
Time Machine has zero deduplication outside of APFS native file clones though.
I.e., I have a 10TB external with a number of different versions of a 1TB photo library on it and a 1.5TB Final Cut Pro Library. There’s an archaic Aperture Library, a Photos Library, Lightroom Classic Library, and card clones from my individual SD cards before import.
Time Machine uses a full 10TB for that drive, but Duplicacy did it in 4TB. That’s because most of the libraries and folders contained the same originals. That’s a huge boon to Duplicacy.
I see no reason not to run both Duplicacy and Time Machine. Duplicacy also gives you the comfort of periodic hash checks to protect against bit rot that Time Machine does not have.
I’ve restored from my Time Machine backups probably 15-20 times in the last couple years. I’ve never restored from Duplicacy, but that’s because of the ease of access. I take comfort in knowing that Duplicacy safely uploaded a copy to Backblaze, as well as created a cold offsite backup on a 3.5" external, and a copy in my local OMV server for me.