I like to preserve CSFB compatibility support for 2G here in Europe, but for those (still) using 3G (WCDMA) within Asia Pacific and Latin America (adopting the APT700 band plan) regions/countries, like you @irvinewade or @BarryK, and looking forward to use VoLTE on their Librem 5 might take a look at SIM7912G-M2 (MDM9240, S2-1085D, Cat.12, M.2 card, Global) as it should be RCM approved (or will be soon).
For the rest of us (including average joe under FCC umbrella) might be that Purism is the only one to provide some update on M.2 card(s) that will be provided or not. Therefore my question here: why or why not to consider usage of THALES DIS AIS Deutschland GmbH Cinterion PLS83-W (GCF Reference: 9540) module (LTE Cat.4 with 2G/3G Fallback)?
Also, MDM9607-0 (LTE Cat.4) supports VoLTE (like within SIM7600G-H R2 module, for example) so expecting that the BM818 M.2 modem variants will do the same is not something to dismiss, but not to forget that:
or