These are fantastic. Straightforward 0603 build, albeit with a lot of parts, flashed with ST-link and JTAG adapter.
There’s a build guide on Westlicht’s Github.
Worked first time (ignoring a single LED I’d placed the wrong way round) so nothing to report. The calibration requires an accurate, precision multimeter…
…and I’d recommend testing everything by flashing it with the TESTER.HEX firmware: