Had a setup years ago with linux2.6 & ardour2 that was absolutely rock solid - never saw it crash or do anything dumb, even running flat out 98% cpu <1ms latency or something stupid…
Currently running ardour4 at ~ 4ms latency on a desktop it’s pretty stable, though I have seen occasional weirdness with daily use for months. The challenge for live gig setup with ardour is always going to be getting decent portable linux setup. You have to go nuts with realtime kernel, tuning interrupts etc to get everything tweaked up right.
Maybe a thinkpad would do the job, otherwise for low-latency, high stability I would advise against usb audio interface + linux/jack. Pretty fraught with problems tuning for reliability below 30ms or so, then weird bugs like audio latency not being consistent when you restart jack ughh!
Well it’s all free software, so if you have a lot of time to mess around with linux at least you can try setting up a working system on whatever hardware you currently own. But don’t go into it unless you feel an the urge to tinker with your computer. Probs best to just buy something if messing with computers doesn’t feel like an end in itself…