[RAZKOM]

I'm in the exact same boat. Look up the BeepBerry. It has the same blackberry like design but uses a Raspberry Pi Zero instead so it actually runs linux. Too bad they're no longer made but you could probably find one second hand with enough digging. For now I just use Termius on my phone but a dedicated device sounds awesome.

[Avamander]

BeepBerry is awesome, my only issue is the relatively low resolution of the screen. But it is very readable in bright light. Tradeoffs, I guess.