I know I am a bit late here but today on a test installation of 20.04 where I follow the development cycle of the next lts version I noted that libnss-winbind:i386 was removed.
This test install is in fact in a active directory domain. Now if I create a new 32 bit wine prefix the uid to name resolution does not work anymore in 32 bit processes. In 64 bit prefixes the USERNAME variable gets populated correctly, but I guess since 32bit and 64bit processes now have a different view of the uid/gid to username/group mapping some applications might get confused.
My question is how is nss accounted in the selection of 32bit libraries. I see that libnss-mdns is available. Also every nss library that comes from systemd seems to be available as 32 bit.
I would suggest including every libnss-* that is in main. I think libpam-* can be ignored since I don’t think there is a 32 bit application around that uses this and is on the list of the still supported 32bit packages (i.e. I am not aware wine does this, which is probably the main reason we still stick with 32 bit)
p.s.: I opened a question here: https://answers.launchpad.net/ubuntu/+source/samba/+question/688146 where actionparsnip proposed filing a bug report.
But I don’t think this is not really a bug but more a decision that has to be made (maybe already done) if/what libnss packages should be availabe in i386