Android Q will include more ways for carriers to SIM lock your phone
Over the weekend, four commits were posted to various parts of Android's Gerrit source code management, all entitled "Carrier restriction enhancements for Android Q." In them, we see that network carriers will have more fine-grained control over which networks devices will and will not work on. More specifically, it will be possible to designate a list of "allowed" and "excluded" carriers, essentially a whitelist and a blacklist of what will and won't work on a particular phone. This can be done with a fine-grained detail to even allow blocking virtual carrier networks that run on the same towers as your main carrier. I'm sure carriers won't abuse this functionality at all.