(answered) Install /e/ on FP5 with newer Security Patches

Yes … but … Installed 3.0.2 official and tried to lock bootloader.

I coined a term “Late Lockers” (by which I mean those who do not perform the lock immediately after install, without reboot as said on the /e/OS install page) … if you take this route there is another reported success Revert back to stock OS and relock bootloader.