Does anyone maintain a list with de-facto support of amd chips and mainboards? That partlist site only shows official support IIRC, so it won't give you any results.
However in the past there have existed very few CPU models and MBs that supported either kind of DIMMs, while today this has become completely impossible, as the mechanical and electrical differences between them have increased.
In any case, today, like also 20 years ago, when searching for ECC DIMMs you must always search only the correct type, e.g. unbuffered ECC DIMMs for desktop CPUs.
In general, registered ECC DIMMs are easier to find, because wherever "server memory" is advertised, that is what is meant. For desktop ECC memory, you must be careful to see both "ECC" and "unbuffered" mentioned in the module description.
For out-of-band ECC, e.g. with standard ECC SODIMMs, all the embedded SBCs that I have seen used only CPUs that are very obsolete nowadays, i.e. ancient versions of Intel Xeon or old AMD industrial Ryzen CPUs (AMD's series of industrial Ryzen CPUs are typically at least one or two generations behind their laptop/desktop CPUs).
Moreover all such industrial SBCs with ECC SODIMMs were rather large, i.e. either in the 3.5" form factor or in the NanoITX form factor (120 mm x 120 mm), and it might have been necessary to replace their original coolers with bigger heatsinks for fanless operation.
In-band ECC causes a significant decrease of the performance, but for most applications of such mini-PCs the performance is completely acceptable.
something like that?