You need three components: 1. SLIC in firmware. 2. Matching OEM:SLP certificate installed in Windows. 3. OEM:SLP key. Note that generated, not official keys can get blacklisted.
Indeed! This was just for the PoC and test latest SLIC 2.5 elsewhere than Server 2019 Std. No real need for this...
There seems to be an OEM:SLP channel, but I'm not aware of any working OEM:SLP key for ServerRDSH in the wild.