Some realms can connect. Also affects public servers.
To reproduce, simulate my network by setting the modem to IPV6 only. Make sure to check if you have IPV6 on https://ipv6test.google.com
Open Minecraft and make sure to have 30 different friends adding you on their realm from different places so the addresses will be different (for chance purposes). Or basically open Hive Minigames. You can also try 2b2tpe.org:19132
Other servers with IPV6 addresses are recognizable by the Minecraft in your side but some are not so fix this issue thanks.
Update: Hello there mod. This should be a bug since we ran out of IPv4 addresses. I contacted my ISP Globe and asked them why is your IPv4 weak? They said "We cannot deploy more IPv4 servers since we ran out of IPv4 Adresses. We have more IPv4 Servers than IPv6. But our IPv4 servers are running at maximum capacity. We suggest you to ask Microsoft to fix their IPv6 in their programmes or play on unconjested times.". Resolution: Sadly playing at 3am does not work too. It's maybe how minecraft read IPv6 addresses are buggy. Please fix mod.
It is not clear why this would be considered a bug.
You have disabled IPv4 connections based on your modem configuration.
Not all servers may have IPv6 addresses. If a server does not support IPv6, the IPv4 address will be available, but if you disable IPv4 then it won't work. If the server only supports IPv6 and you cannot connect, this report might be a duplicate of MCPE-66233 but there is not enough information in this report to determine that for sure.
If you can get the issue to occur without using non-standard network configurations, please provide a complete list of steps to reproduce the issue along with the observed (including error messages) and expected results.
This report has been temporarily closed as Awaiting Response. It will automatically reopen when you comment with new information. Please be sure to provide all requested information. Reports that do not contain enough information may be closed as Incomplete.