Well, so far I think I’ve narrowed it down to two LTE modems that work with the Banana PI R3 and an eSIM.
So far, as of this post, it appears the Fibocom Wireless Inc. L860-GL-16 is what you are looking for. Searching wielessjoint.com you’ll find some of my words on this as well. I still need to ordered one and will give it a shot! the Fibocom Wireless Inc. FM101-GL-12 also appears to support eUICC. From what I can tell, the LTE modem needs to support eUICC to support eSIM. The thing is, nowhere on the internet have I found anything about configuring eSIM in OpenWRT.