Using static groups to grant unprivileged users device access is a concept which has been discouraged for a while.
We should document that explicitly, mentioning what the problems of this approach are.

We should also document the replacement mechansim based on uacess/udev/logind. How those pieces fit together, like tagging the devices via udev rules, logind applying the permissions for local and active users etc.

We should also give some hints for people writing udev rules (e.g. for package maintainers or upstream developers). E.g. if it is ok to use TAG+="uaccess" directly or it's better to use ID_* variables and letting 70-uaccess.rules do the tagging.