I get what you are asking for but I don’t think it is even necessary to have a list of users on the client in the first place using the MPA approach. I would guess the list of users is just available to the server, which pre-renders HTML out of it and provides it to the client.

I don’t know, but for me it just worked when I clicked on the google wallen option. Since I don’t have google wallet it just downloaded the pkpass instead.

I use fWallet. Works just fine, but you will have to be able to download the pkpass file and import it into the wallet: https://f-droid.org/packages/business.braid.f_wallet

If you are interested try Localsend, its even less effort than sharing via a messenger and its peer to peer. You can enable auto downloads for trusted peers then it will be sent directly to a folder of your choice once you send from your phone.