I am still using my FP2 with a recent LineageOS. Since several months I have the problem that after a reboot the SIM code dialogue, where you give the code, comes very late. Everything started, already new messages via WLAN are here but the code dialogue is still missing. Sometimes it helps to push the on/off button two times (screen off and screen on) to have that window.
Any idea to fix this problem?
I have the same problem with my FP3+ running /e/OS (Android 12). As to how to fix it fundamentally, I don’t know. @AnotherElk speculated it might also be related to carrier (network).
In my case, the reliable workaround is to let the display fall idle (black) by itself (switching it off will not deliver the following solution in my case), then wait 10 seconds before I activate the display again. Then I see the SIM PIN prompt instantly.
Thanks for your answer. I don’t think that could be a carrier (network) problem - I tested it with different SIM cards from different providers.