Current uptime is 58 days! We have multiple power cuts a day but these use so little power, they’re very easy to keep online.
It’s been “set it and forget it” with how reliable they’ve been (probably need to do updates though).
edit: to answer your question, the ASIX usb nics have been stable under Linux in my experience and should work fine for a x86 router setup, but I haven’t tried that with them. I had one on a thin client for over a year before I upgraded to a Lenovo tiny.
edit edit: Relevant user experience I found some years ago: https://blog.kroy.io/2019/12/08/the-wyse-5070-a-perfect-little-vyos-device/
That’s for the pentium version, which I had some years ago but sold to another member here. The pentium models were strangely less stable than these celeron ones. It’s probably because software support is much more mature now for these platforms.