I'm currently on 1.16.4. But I can't connect to my friend's realm that I was able to connect a week ago with hotel wifi.

I'm now using stable ethernet instead of wifi. However, even though the loading screen works and the bars are moving up and down between left to right, it just refuses to connect. Single-player mode is not affected as I can still access my own worlds and create new ones.

I've also contacted the realm's owner and he said he can connect to the realm with no problem. It seems that there is something I can't fix.

Edit and update:
The "solution" given in the link is to press cancel for the first connection and then reconnect for a second time. In short, it works, but it takes longer than 10 seconds (for me) to load for the second try so needs a little bit of patience.