True enough

Well it‘s true that one can use RSA, which is still save with keys big enough, but if someone wants so save some extra computing power and time ed25519 is the way to go.

It depends.

• Do you want to have access from outside of your network or do you want to host several services to the public (in the future)? Then I would recommend buying your own public domain. It doesn’t need to be a TLD.
• Do you only want to use your services privately? Then use home.arpa as explained in the rfc 8375.

I would discourage you from using popular but misleading „local“ domains like .lan, .local, .home etc.

That is because those domains might already be available in public. So when you use .lan for example your dns-queries might be forwarded to the public never resolving your privately hosted services name. It could also „leak“ private network information like on what port you try to access a service and how that services name is.

Also you should highly evade .local which was also my mistake. Some services like MulticastDNS i.e. apple bonjour service rely on this domain. If you would use it unknown problems might be frustrating you.

So if you host everything private, go for .home.arpa.