Yeah no.
tech2but1
Pointless re-inventing the wheel. Help with some existing project instead. NPM needs some help, few bugs to fix and a little bit of added functionality to make it perfect.
AdGuard Home.
Aside from other stuff mentioned here about email. I always assumed I'd become a target for spam that I'd have a harder time filtering out to the point it stops being worth it to have a custom email address.
Can't work out how or why hosting it at home would mean more spam? Your email address gets on a list that gets pulled by spam merchants, hosting it at home doesn't make any difference here.
Same with Bit/vaultwarden, all clients grab a copy of the vault from the server when they sync so if the server is offline all clients still "just work".
Chances are your router can have a fallback DNS.
Chances are it can't. You can probably set multiple DNS servers (anywhere, not just routers) but they aren't a primary/secondary sort of deal. Most traffic might be weighted towards the first one in a list but you will find traffic still hits the others.
Build a webpage, host it on the device.
I'm going to say sort of all of the above, but not just across the whole board. Some services I host because I want a better service than is available elsewhere.
For example I host AdGuard Home and OPNsense because it's better than my ISP supplied router and I get more out of it so that's better service. I host Immich because I don't want to pay Google to store all my photos when I have a server sat here that's quite capable of doing it so that's cost I guess.
Ask the reddit devs, that's basically how reddit started out!
The correct answer has been given a few times here, split tunnelling.
But your idea is mental. If your IP changes and access is locked down by IP address how do you expect your phone to connect to your server to tell it about the new IP if it can;t access the server due to the fact it hasn't got the correct IP in the allow list?
Well it won't. You either tell it to assume that say oldest is always source and if there are identical files then you get asked to choose.
Most definitely a scam. Website shows a different URL to the domain and the phone number is formatted completely randomly.