Add PAM user in Proxmox

Create user in OS

groupadd <group>
adduser -g <group> <user>
passwd <user>
mkdir ~<user>
chown <user>:<group> ~<user>

Add OS user to Proxmox

pveum user add <user>@pam
pveum user list

Add role to user

pveum acl modify <PATH> --roles PVEAdmin --users <user>@pam

For example

acl modify / --roles PVEAdmin --users user@pam

References

Add pam user to pve admin group?
users cant change own passwords
User Management