I ran into the same problem some months ago when my cloud backups stopped being financially viable and I decided to recycle my old drives. For offline backups mergerfs will not work as far as I understand. Creating tar archives of 130TB+ also doesnt sound like a good option. Some of the tape backup solutions looked to be possible options, but are often complex and use special archive formats…
I ended up writing my own solution in python using json state files. It’s complete enough to run the backup, but otherwise very work-in-progress with no restore at all. So I do not want to publish it.
If you find a suitable solution I am also very interested 😅
Do you want to supplement your usenet sources? If so, what type of content/language are you looking for? Do you have any proof like screenshots of the old times left?
Things that should be answered before anyone would consider giving away an invite, because that is also a liability.