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.