There is still an unresolved bug in the linux kernel that lets for some users vanish the #bm818 modem of the #librem5 from the internal usb bus.
https://source.puri.sm/Librem5/linux/-/issues/303
Problem is that it sometimes doesn't re-appear by itself and if one doesn't notice (the icon in the top bar of phosh changes and shows no connection) the phone is not booked in and doesn't receive calls, sms and isn't connected to the internet.
I adopted some of the solutions mentioned in the issue, added the service and scripts to bm818-tools in https://source.puri.sm/ChriChri/bm818-tools/-/tree/watchmodem-next#watchmodem and now there is a package L5 users can install.
You can find it in the pipelines of my repo.
Feedback is very welcome!