
Assuming datareader is required, the following result was found.
Mapping. Map the login to the database they will have access to. Tick the boxes for role membership next to public and db_datareader. Confirm by clicking OK. You should get something like the following: Database-level role names from...

bc1qf6elrdxc968h0k673l2djc9wrpazhqtxw8qqp4
0xb038962F3809b425D661EF5D22294Cf45E02FebF