For the past 6-8 months I’ve been using Cloudflare-dns [dot] com as DoH DNS on Android 13 with no issues. This past week I noticed it stopped working with an error: Private DNS server cannot be accessed.
More screenshots:
https://i.imgur.com/XI1v2qh.png
https://i.imgur.com/7NOjZfp.png
Followed this guide saying to use cloudflare-dns[dot]com:
https://www.androidpolice.com/android-dns-over-https-mainline/