I am one of the guys that is often plagued by the 2.75 G problem, i.e. after a boot you are stuck at 2.75 G which won't give you any mobile data.
I found out more details and a solution that works for me. Context: I turned off all 5G bands under "Mobile Network" | "Enabled Bands" some weeks ago. The interesting part is that after each reboot the "Band 1" under 5G is automatically reenabled. (Is this intentional or is this a one-off programming error?) And when I disable again the "Band 1" (i.e. no 5G bands as I intended before), enabling Mobile Network gives me 4G with data in just a second. Does this make sense? Can this lead to a programmatic improvement?
Great finding. I can reproduce something similar. I'm often stuck in 2.75G after boot. Previous workaround was to just shutdown, what a few minutes and try again.
Now for me the trick is
* disable all 5G bands
* disable mobile network using phosh top left button
* enable it again
* now the 5G "Band 1" is selected again (for some reason)
* turn on mobile data / roaming and I have 4G (in 1 out of 1 attempts)
@sve band 1 being enabled automatically is a intentional. at the moment the firmware does not allow to disable all bands, so it needs at least one enabled from each network type. but it does not break anything so it should still work fine and disable 5G even if band 1 is marked as enabled.