BLUF: I installed Qubes 4.1.0 on the Surface Pro 4, which went fine until I couldn’t update Qubes via Ethernet due to no internet connection. This happened via a USB-to-Ethernet OTG adapter and the Surface Dock 1.
I think PCI troubleshooting is the way to go, but I have no idea what CLI commands in a dom0 terminal emulator to use for diagnosing. IIRC, an option containing Marvell is autoselected (which aligns with this page form the Linux Surface wiki.
Some background details
Even though the WiFi works and I could just get the updating of Qubes after installation, I wanted to resolve the Ethernet issue first - it wasn’t clear to me the problem would “go away” based on first principles after updating Qubes OS anyways.
According to this in Qubes 4.1, sys-net is supposed to “just work” when the internet is connected.
Because I can’t get an OTG Ethernet to USB-A adapter to work with the Surface Pro 4, I’m inferring that there’s nothing wrong with the Surface Dock 1 (which is what I used to install Qubes OS from a live USB).
Right now, this is my only issue holding me back from preparing a HCL submission for the Surface Pro 4. I though that I might as well see how far I could go with the Surface Pro 4, since the Surface Pro 3 and Surface Pro (2017) are on the HCL but for much older versions of Qubes OS.
I wasn’t considering using Qubes OS full time on my model of the Surface Pro 4 (i5 version), since it only has 8GB of RAM - which anecdotally isn’t enough to simultaneously open 2-3 VMs for serious compartmentalized work. Once the HCL submission is complete, I wouldn’t be keeping Qubes OS around as a long-term bare metal install, but I could reinstall Qubes for reproducibility if others had issues during installation. (I will eventually have to if the Pro 4 ever gets more system/firmware updates after July 2021)