nanoCH32V203 VS evsieve

If you are willing to try r/RISCV ones, then nanoCH32V203 (with two Full-Speed interfaces) and nanoCH32V305 (with one Full-Speed and one High-Speed interface) might be enough.

There are dual USB r/RISCV boards with GPIO pins exposed, like nanoCH32V203 and nanoCH32V305.

Another alternative is to use dual USB MCU board like nanoCH32V203 as USB CDC relay.

RISC-V boards cost $3-$6 depending if you want high speed USB or full speed one.

Their earlier boards like nanoCH32V203 and nanoCH32V305 were more user friendly, one could flash those via USB without WCH-Link.

Muse Lab has MCU boards like nanoCH32V203 and nanoCH32V305.

The same form factor as nanoCH32V203, but with more RAM and storage, also one of USB interfaces is high speed and SDIO is native this time. Comparable to CH32V307 boards, but lacks ethernet port.

Speaking of hardware there is very nice $3 RISC-V board that would fit well USB to USB converter use case. No keyboard firmware is ported to it yet.

Same with evsieve: I can see the keys I press, like in wev, but the remap doesn't work for the keyboard or the mouse:

My best suggestion for you is to leverage evsieve: https://github.com/KarsMulder/evsieve

There are many other software tools such as https://github.com/jtroo/kanata and https://github.com/KarsMulder/evsieve. The main difference with 𝑥MK is that you can use native QMK and ZMK.

Ironically I know you can do this in i3 and xorg/gnome using xmodmap or editing the xkb file. I'm pretty sure wayland compositors should be able to read xkb-compliant files but the recommended way of loading that in is probabaly different between various compositors? You could also use a "second generation" interception tool that works at the event device level.

You might want to try evsieve, it even has an example about toggling devices and it concludes with a hint on how to get this to work for 2 VMs.

Evsieve is amazing in general you sould check it out 🙂

evsieve has solved that for me, as the virtual device created is always available; it starts when I log on my computer and stay open forever.

evsieve can remap. I haven't used it yet but you can find it here: https://github.com/KarsMulder/evsieve

If this feels a bit limited (you have a few predefined options), there's also evsieve. Which allows you to do a lot more (like selective key pass-through, shortcuts, etc.).