This is easy enough, one of the existing Admins adds your account to the NextCloud "Admin" Group
Unwanted emails avoidance
Unless NC has fixed it recently there is an automatic rule in the Registration module that all members of the NC Admin Group get sent an email to confirm that a new user has been created. No way of turning this off.
However what you can do is to create a rule in your email client (Protonmail etc) which automatically moves all such emails to a particular folder.
See this screenshot of the Select statement to identify all such emails
Deleting user accounts.
Record all deletes in the spreadsheet in this area of Tech Circle's area in NC - Tech_Home → Tech_Internal → Applications → NextCloud
In same folder is the Googlesheet file which recorded new account setups etc prior to the introduction of the Registration module
Creating a New Group
Group naming RW suffix allows for RO etc if things change
Manually reset a password
Create a new shared area for a new Team, Circle, Action etc
Upating banner info in NC top level
special areas - media library, and integrators area