350+? I'm seeing the M6 listed for £160-200!

Yeah, I had a similar experience getting my Orange Pi 5 Pro to just allow me access to I2C (though once you figure it out, it's a lot easier to also get stuff like GPIO, SPI and so on to work).

In fact that's the general problem with the chinese SBCs compared to the Raspberry Pi devices - their support software, documentation and general support out there on the Internet from other users is a much weaker, at least in English - to get that stuff to work I actually on my Orange Pi I actually had to get an Ubuntu for Rockchip and then figure out how to manually add a device tree overlay with the required devices enabled whilst I believe the Raspberry Pi just has a utility that does it for you.

HOWEVER, the user who had asked for advice higher in this thread only seems to care about hosting, for which you just need "normal" Linux functionality not the embedded side of things, in which case those things work just fine even with just ARMbian - as far as I can tell all those manufactures do make available a Linux distro for their devices which supports the built-in peripherals (most relevant for hosting, wi-fi and when present ethernet) and does the normal things a desktop Linux does. That said, they quickly stop pushing out updates to it, which might be a problem.

This is why I mentioned Orange Pi and in another response suggested general Chinese SBCs - if all you need if run-of-the-mill Linux server functionality in a cheap platform, those probably suffice.