After the device got replaced, I started anew, this time carefully following ✏ FP3/FP3+: Complete guide for installing LineageOS
Because last time things went south (assumeably) after issuing
fastboot flash boot <img>
I opted for the variant without flash. That command answered
Sending 'boot.img' (65536 KB) OKAY [ 2.106s]
Booting OKAY [ 13.808s]
Finished. Total time: 18.006s
The guide states “Now, your Fairphone should boot into the recovery.”, but it doesn’t. Instead it boots normally, i.e., I’m unable to get in that recovery menu.
Again I tried different recovery images (feeling safe about this without flash), including one that previously (in August) worked just fine. The recent img I used is https://download.lineage.microg.org/FP3/lineage-19.1-20221016-microG-FP3-recovery.img
What could be the reason why booting into recovery no longer works? Apparently several folks had been successful using that guide.