I am a very cheap bastard, and I have gigged with much more primitive Ubuntu Studio-based rigs going back to about 2015 at least.
My process of Zynthian adoption was, I tested it headless first, and was impressed at the stability. Then I built myself one based on my own Teensy controller, and again, the only thing I didn’t like was my own inability to program the rotaries so they turned on a dime. Required two dimes (detentes) to make the u-turn.
I do not see an issue with stability, going back years. Both my homebrews and the V5 I got in the last year, I leave them idling for weeks at a time, come back, it’s still ready to go with the patch I had set. Like I said, I’m a cheap bastard, and I would not have spent on the hardware if I wasn’t pretty damn sure about the software.
That being said - in the end, this is still a Linux computer that runs C code, and the fundamental Unix philosophy is to give you all the tools to shoot yourself in the foot, possibly give you a warning prompt if possible, but generally speaking, you are perfectly able to run sudo rm -R / at any time. Part of my stable experience, I’m pretty sure, is that Dexed, Pianoteq, ZynAddSubFX and the occasional soundfont file have always taken care of my needs. I have definitely had the experience of loading up some random engine and having it go sideways. Hence my interest in the problem snapshot - I’m positive it reveals a bug that needs fixing.
If there’s a weakness, or weaknesses, in what gets shipped with each OS, it will be the many lurking bugs in the many Libre engines that the core team are only implementing in the Zynthian UI - unlike a Roland or Yamaha device, most of the programs that actually generate the noise on a Zynthian already existed before it and will continue to exist (and be available to run as a standalone program/plugin) if Zynthian ever dies.
Capitalist devices will always include guardrails, some well-advised and some just a matter of charging you more for that feature. Zynthian gives you everything with only minimal guardrails; likely it will never be for everyone, even if it reaches the point of being objectively just as good, sonically, as anything else on the market.