I’d like to add that for future endeavors, a preferred modem family should also be selected. There are now more options available than before but they can be finicky and need support - and instead of one single supported modem, a family line would be better. Some future proofing for “LTS phone”.
As far as I’ve kept track (which is not as extensive as some), I think the Quectel line (what was already tested via EM12-G and was preceded by EM060-GL) would be a good fit. There already exists linux support and the line (meaning here variations that use the same size and commands but have increasing features) has variants for different levels of use and price ranges. The current L5 size (which could also be made bigger to allow for current and bigger sizes) doesn’t have a full 5G card at the moment but there is new RedTop-17 spec model that may allow for upgrading to 5G already - and it seems likely there will be future models. I think this is important for the longevity but also to give options for upgrading the modem, from about 40 to 400 coins (€,$,£).
As has been seen, options in this area are needed, but they also need support to get full and perfect use, and that is why a clear choice would be good for concentration of efforts (while not excluding any other potential modems… or any other cards used in m.2 slots). Newer modems would also help a bit with battery life. I’m not aware if there are any major differences in “blobbiness”, but that should be moot, given L5 structure. 4G antennae is the minimum and alternative choices could be to include 5G regardless of modem (or even pre-emptively option for even 6G [the additional freqs at around 7Ghz, not all]) or develop a changeable back cover that has that additional antenna (but that’s theoretical and a bit iffy).