Regular 3.5 inch hard drives, hundreds of them, with some software raid to deal with dead drives. All connected by USB because spinning rust can barely fill USB3 bandwidth anyway.

This setup is cheap to begin with (just $50 gets you your first few TB's), and scales well (127 USB devices per host)

I don’t think many hobbyists use LTO - for backups, being offline is a huge advantage, but for most hobbyists, it’s an issue. A lot of LTO tapes are written to never be read again. The closest thing to a lot of HDDs would be a tape library and, if a single LTO drive is expensive, a library is eye watering.

You can look at the /DataHoarder subreddit, as I see people usually buy secondhand LTO4-LTO7 tape drives and libraries, which are affordable. Datahoarders use dozens and hundreds of cartridges for archiving/backup purposes or for making fun playing with tape drives.