The difference between the "unbuffered" ECC DIMMs (ECC UDIMMs), which you must use in desktop motherboards (and in some of those advertised as "workstation" MBs) and the "registered" ECC DIMMs (ECC RDIMMs), which you must use in server motherboards (and in some of the "workstation" MBs), has existed for decades.

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.