In your comments you mentioned your host is gonna be truenas or unraid, and about 3TB of data to backup. I would recommend backing up to external/hotswap hard drives, which is what Ive been doing on btrfs and my soon to be main truenas scale. Around 10 years ago I scored a dell lto3 tape auto loader from work. It was interesting backing up to tape but after 5 or so years of using it i got rid of it. Biggest painpoint was the backup software. I settled on bareos which was fine but clunky to setup right. I had to write scripts to automate ejecting tapes from the autoloader and restoring files from backup was annoying, especially when backups spanned multiple tapes. Maybe with lto7 these days things are better with that new lto file system and less tapes for your 3tb of data, but youll still probably end up using bareos. If youve got the time and money id say go for it, it was a fun learning experience and initial novelty. Im not sure id go back to tapes personally though.

you can buy LTO tape drive like dell on ebay, just make sure seller will dump how many hours were written with device. when you will have device you will need to connect somehow to motherboard - for example you will need sas controller which can cost like 100$ on ebay. next step would be choosing os - you can go with debian like system or centos, on github you can find ltfs repository (if i good remember developed by ibm guy? please correct me if im wrong). neext step is buying tapes - good source is amazon, for example 30eu for 2.5tb lto 6 tape (included taxes). good luck!!

ps. about which lto drive you need it depends on your needs, if 2.5tb per tape is fine then go with lto version 6…

for more you can ask on r/DataHoarder

Tape is a nice option, but it makes sense if you need to backup a lot of data. I personally have a local NAS, which is used as a backup target, and another one for offsite. You will need a library, tape drives, SAS HBAs. You should plan first and then buy all the equipment you need, As mentioned, you might consider m-disc as an alternative. In case you want to play with Tape, you can test Starwinds VTL. https://www.starwindsoftware.com/starwind-virtual-tape-library

https://youtu.be/f6vhrbD9WkA?si=VyAFF8INKBs75FUy

I saw this a few months ago. Might be of interest

If you wait long enough, you’ll find an HP 1/8 G2 LTO-5 SAS autoloader tape driver somewhere between $250-$350 on eBay. That gives you 12TB uncompressed or 24TB of hypothetically compressed storage. Then buy the absolutely cheapest SAS card like a Dell H200E (which goes for about $25) and you’re all set. Don’t forget the appropriate SAS cable.

And, this combo works perfectly with Veeam Community Edition.