Actually, with the work done on box86/box64, you might be able to get stuff running well - last I heard, they got triple A games running around 45 FPS on Asahi on Apple M1.
However, it would be totally unsupported, and who knows how well the Apple M series optimizations will work on another member of the ARM family. (Although, I wouldn’t be surprised if it’s been tried on Ampere at least once.)
Really, the biggest issue is probably power usage - I don’t know if it’s enough to increase your power bill significantly, but it would definitely consume more power than say, an i7. This is due to Altra CPUs really being more for server usage - performance per watt will likely be better overall for those kinds of workloads, but you’re probably not going to make full use of the hardware. These systems are really more of server dev kits than daily drivers.
For a desktop, I’d just recommend a PC with a high end consumer grade CPU like an i7 or Ryzen 7.
Not necessarily. It’s currently on the latest ESR version. I use the repo version on my laptop (stable) and testing and don’t have this problem.
In recent years, Debian has gotten a lot better about keeping stuff on the current ESR version.