1.- You get a "nice PLMN" for the network and assign phone numbers (and manage key material) only after Ham Identification. DMR Style (at least here in Spain)
2.- Most of them will refuse to join any Private SA network that does not use SUCI and encryption (in my experience). If you have a "nice" PLMN, they will connect. What a "nice" PLMN is varies between modems, the testing PLMN is a safe bet :)
3.- Also gone down this rabbit hole. eSIMs must be signed by a GSMA authorized key, and they are picky. Osmocom people have relationship with someone that signs profiles for them (for pay). The crypto is quite straight forward to do offline, eSIM profile distribution not so much. Key propagation from generator to core network and final client (ue) would also be a challenge. Another option is using the testing certificate, it should remain active in most modems for certain PLMNs. I have yet to test this, but work gets in the way
There is a variety of open software and COTS hardware that could fully power this network. The client side is the hardest part, especially if you want a phone.
PC modems on a Linux machine are more manageable (But expensive, let's wait a few iterations on RedCap maybe). And SIMs with ADM keys can be purchased from different sources
2.- Most of them will refuse to join any Private SA network that does not use SUCI and encryption (in my experience). If you have a "nice" PLMN, they will connect. What a "nice" PLMN is varies between modems, the testing PLMN is a safe bet :)
3.- Also gone down this rabbit hole. eSIMs must be signed by a GSMA authorized key, and they are picky. Osmocom people have relationship with someone that signs profiles for them (for pay). The crypto is quite straight forward to do offline, eSIM profile distribution not so much. Key propagation from generator to core network and final client (ue) would also be a challenge. Another option is using the testing certificate, it should remain active in most modems for certain PLMNs. I have yet to test this, but work gets in the way