So I have to post a self correction. Today I figured out how to get a private DNS to work on the Mudita, so I guess Private DNS is working if you have ADB. The commands are:
adb shell settings put global private_dns_mode hostname
adb shell settings put global private_dns_specifier dns.adguard.com
You can just change dns.adguard.com to whatever your DNS server is, and that can be used to block any telemetry on the phone.
Having looked at the logs over the past month, the Mudita is a very impressive device from the standpoint of privacy. It doesn’t make a lot of connections and when it does these are almost always from user actions. (The Sentry code excepted.) I agree that there is some worry about whether Mudita (as the manufacturer) could link up IP addresses to MAC or other identifying information. Hence why a lot of people concerned about this have moved to a “zero trust” model where trust is baked in (as much as possible) and options are available to disable things in case the user is concerned. The Private DNS is now a workaround.
One other possibility is to simply have dialog available on set-up. The Supernote eink devices (which are highly regarded in the eink world for community engagement and support) supply a dialogue like this, for example:
