FP4 bought from murena in 2023 stuck at e/OS 1.12.3 - s

Any given software thing can fail or hang anytime. You could first try to get the updater rolling again as described here …

@ltdm, too.

As your phones are on the stable build type, at some point the updater should offer an upgrade OTA (= over the air = via the updater) to /e/OS based on Android 13 (T).