A mainboard died. It was exchanged for the same board type (same bios and config, as well, also a new CPU but of the same type).
The hard drive is encrypted with bitlocker (on Win10 Pro v1903) and I use an fTPM (Intel PTT) + PIN. I had expected to need the recovery password after exchanging the mainboard, as I often did with discrete TPMs after a mainboard change, but here, I didn't need it. How come? (asked the same on MS Technet)