One thing I'd like to add that might be useful (or not!). When I was using Tumbleweed (between March and July 2020) on my SSHD, everything worked fine and the boot entry was created properly whenever I changed any settings or updated. The SSHD had Manjaro, Ubuntu, Windows and TW, all in single separate partitions. If it was my EFI, it would have failed there as well, I guess. What other software is invovled in the process of making the boot entry, apart from efibootmgr and libefivar1? Could it be something already fixed?