One of the issues that anyone with Bru faces now is that, if they have ver 3.x, then they can no longer upgrade to Argest 4.x. And that’s important because ver 3.x does not work on macOS 10.15. And any new Mac you buy now, will have macOS 10.15 pre-installed and which cannot (presumably ) be rolled back, nor can the Mac be booted with macOS 10.14.
So, if one is using Bru 3.x on an old system, then that needs to be replaced with an old system too. One option is to buy a refurb Mac 2018/19 model on the Apple Store. Or, of course scour eBay or some other such site for an old system. Outlets like OWC could be having good ‘open box’ deals on 2018/19 models too. But the time is literally, now, for this purchase.
Alternately, since Tolis is closed, one can possibly ‘borrow’ a copy of Argest for someone who has it, and then one is fine with a new Mac. But any compatibility issues with older Bru 2.x and Bru 3.x catalogs with Argest, will not be supported since Tolis isn’t functional.
The situation will get more complicated next year or maybe 2021 when all new Macs ship with macOS11 which may or may not work with Argest.
Migrating from Bru archives to LTFS using a good LTFS app is a possibility for the original poster because they have all the data on drives as well. But for someone who doesn’t, the laborious task of restoring their Bru tapes to drives, and then writing them to LTFS looms large, and needs to be done within about the next 2-3 years.
Happily though this might be a good thing as the number of tapes will reduce drastically. Like, 12 or more LTO-4 tapes will be replaced by one LTO-8. Or even with LTO-5, 7 or more LTO-5 tapes will be replaced by one LTO-8. If one waits for LTO-9, then there number or tapes reduced will be even more.
But migrating LTO looks like is going to be a necessity as older LTO tapes become unsupported by newer LTO drives. Already LTO-8 tape drives can no longer read LTO-6 or earlier tapes. So, one necessarily has to own and maintain multiple LTO drives. And check the older ones from time to time to ensure that they still work.