That answers the Linux part of your question
Many installation problems show up in the handling of USB3 and related quirks; I have a lovely AMD 8350 system that I can't install from USB onto because of some XHCI problem. The USB stick will boot the kernel, but then the kernel can't properly handle the USB stick after it has booted and can't see the installation media. I suppose I should bite the bullet and burn a CD to boot from, which should fix it.
I wonder how far a compatibility layer for Linux drivers could go to help other UNIX kernels' usability. Maybe the Oxide folks know more of what would be involved in such an effort.
This isn't very interesting. It means you're constrained to the Linux design decisions, and you're wasting time debugging mismatches and poor design decisions.
The right solution is actually explained the headlined WWW site, where Peter Tribble points out (in the About page and in the Use guide) that the significant constraint is that xe does not own the actual physical hardware to develop against. It's the usual story with small projects: good donated hardware, and developer time (and workspace, and food, and water, and housing, and electricity supply (-:), needed.
I would expected CDE as a first class citizen and maybe OpenLook.
And it says that it it maily for 32bit SPARC and 32bit X86 and later that "Important: 32-bit hardware support now completely removed.".
I do include CDE and Open Look (the window manager and toolkit, at least). In both cases the add-on tools that were present in Solaris (like the whole of the DeskSet suite) aren't available, because they were never released in source form.
https://tracker.debian.org/pkg/xview https://tracker.debian.org/news/1000764/removed-32p14-282-fr... https://bugs.debian.org/911787
But there is a 64-bit port (which I ought to bring in to Tribblix)