nanoCH32V305 VS ChibiOS-Contrib

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.

There are RISC-V MCUs that have two USB interfaces, but those are not supported by QMK yet. I tried some of those boards in kite project.

Kite has standard shortcuts option too, but it runs on dedicated MCU board, not host PC.

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

u/Bounty1Berry is exploring RISC-V nanoCH32V305 board, but it's a new board that is not supported by (Q|T|Z)MK yet, so not really go-to option at this stage.

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.

It runs on nanoCH32V305 dual USB r/RISCV MCU board.

First u/KarlK90 ported QMK, TMK and ChibiOS to GD32VF103 and used it in YAEMK.

Some of the work was upstreamed: https://github.com/ChibiOS/ChibiOS-Contrib/pull/248

Specifically for that MCU, there’s some initial support in ChibiOS-Contrib: https://github.com/ChibiOS/ChibiOS-Contrib/tree/chibios-20.3.x/os/hal/ports/LPC/LPC11Uxx

In regards to drivers for a processor or microcontroller, you may want to check out ChibiOS's HAL which provides non-blocking APIs. See here and here for an idea of what architectures are supported. I use this HAL whenever I can; it's clean and versatile in my opinion.