My understanding is as follows:
A new user accept the terms at registration (no opt-out) and afterwards this acception is shown in his profile, but here it may not altered to not accepted anymore. So I gave the field a "Read Only" bt it doesn't work as in other fields. What I have to do? Or what is the idea behind this system field?
(if I set this field to "Required", I cannot save the profile anymore, if the acceptedterms is checked, only if it is unchecked - ?)
EDIT: I find a solution. In config I activated "Mandatory fields in the user administration" and set acceptedterms to required. Now a new line appears: "Accepted on 27.06.2019 11:04." Great!