There is very little information on the Hall Effect sensors on these modules!

https://www.youtube.com/@UberMicroRepairs is one good (excellent!) source on installing these modules (problems and correct ways on installing them).

I forgot to say the exact modules in my post. They are the Ubituitous Ginfull sensors. These ones have L-8L (yellow) or R-8L (black) on the PCB, which is red and black text on it. Early Ginfull modules have problems with jitter (a non-issue, really), which was fixed in later batches but at the same time introducing an even worse problem, huge lag (presumably because of the filtering they’ve used to counteract the jitter). But these [LR]-8L’s should be better in terms of lag again.

The chips itself have markings “93L35”, they are 6-bin chips and tiny. I could not find their datasheets.

The well-known problem with these Hall Effect modules is that they only allow adjusting centering. So they will “work” in practically any controller out there, but more often than not there will be huge lopsided deadzone(s) caused by the H/W in combination with the previous calibration data. The SC is not that bad since it has some intelligence (I’ve deduced by test) but this can bring it’s own problems.

I’m not aware of any of the problems you’ve mentioned (but haven’t personally used DIY Hall Effect sensors in any controllers before).

There are calibration boards out there, which add a calibration mode between the controller and the module to also get the full range of movement in use. But Steam Controller has no room for those (the shell already has indentations for soldering spots and a mechanism for the back button, so this is feasible only if one is willing to sacrifice a back button or mod around it). Asides from centering and calibration (which needs to be manual!) there is no large issues AFAIK. They are widely installed in modern console controllers. PS4 and PS5 contorllers can even be calibrated (by undocumented USB commands), so they don’t need the boards.

But as far as I understand Linux doesn’t support freeSync yet which is a shame.

Linux does and has supported FreeSync jsut fine for several years now.