Also, dont spend more on your sources than your actual transducer…
I have a big post about the server here.
You just need to have mobile data or I guess using public wifi also works if you dont have mobile data. And then using for example Tailscale will allow you to access your NAS from anywhere in the world even if the NAS is not open to the internet (no ports open on it), can also use a VPN on the NAS but that is much more complicated and I believe needs one port open so less secure.
Do note that in that post I wrote I did not have nor knew about tailscale so I just use the cache download function there. I am likely going to buy myself an Orange Pi to use as my VPN (PiVPN) (Along with DNS and some other stuff to offload from my actual NAS) so I can have it on another device for an additional security layer.