fritzhelp.avm.de/…/hilfe_internet_public_dnsI found this guide for the fritz!box to set up a fallback dns, I think it should be on by default as it is on mine but I would read the article just to make sure
I’m not sure if this is a response to my comment but the article I linked isn’t about setting a secondary dns, the fritz!box has a function that allows it to temporarily change the dns (usually to 8.8.8.8) if the specified dns isn’t working. It is separate from the “normal” dns settings.
So a reverse proxy is a way to manage subdomains? I read somewhere that it allows multiple different services to be hosted on the same port and I think I know that that is probably a lie.