mmobder You're wrong in general sense
You're right, I can't say it's really triggered by that event but just that it's triggered when this event happens (charging or connecting cable - whatever releases this "when").
mmobder If that's your case, take a look if you have any configuration (in a user or system app) "bound" directly/indirectly to this event.
For example, in Syncthing app there is a "run condition" to run only when charging.
I have no idea what's the real reason for this behavior. There are no configurations that suggest this behavior, not in system apps nor in any third party app. There's no "only when charging" preset in any System- or app preferences, and all system connections to different servers are left as they are at factory setting - everything set to the default graphene-servers, no change to google or opt out. Also there are no active Play Services and just a small couple of (mostly privacy friendly open source) user apps installed.
mmobder as usual, one must check faq/ug in the first place https://grapheneos.org/faq
gstatic is mentioned couple of times there
gstatic is mentioned only two times in the faq namely in relation with changing the default server for connectivity check or Attestation key provisioning from graphene-servers to the standard Google servers. As written, these settings are left as the default to the graphene servers. And the connection logged Rethink is always www.gstatic.com and not connectivitycheck.gstatic.com or randomstring-dnsotls-ds.metric.gstatic.com or something like that.
sebastianha I noticed that they occur often in the same second when there is a request to "remoteprovisioning.grapheneos.org"
That's interesting indeed. In fact The Rethink log almost always shows a connection to remoteprovisioning.grapheneos.org at the exact same time, when the first trial connection to www.gstatic.com is triggered. (I saved some screenshots of the log from time to time.) But there was at least one occurrence when no other connection was logged during the charging process, only the ones to www.gstatic.com.
So, I would really appreciate getting an idea how to find the "culprit".
mmobder I've just put the phone on charge and there are no requests.
What's your preset for the USB-setting? Here it's charging only when locked. Maybe I try different settings for the next charging cycles to see if there's a correlation.