Connect two remote computers

I am looking for a way to connect to e.g. my mothers computer (Linux Mint) in another part of the country, so I can help her with technical issues. I need a remote desktop solution, so that I can see and show what I do.

Neither computer is on a network with a static ip address. If necessay, static ips can be bought, but I would like to avoid that.

Is there a (simple) workaround?

Can I set up a direct connection without static ips?
Can I setup a rented VPS (e.g. at Hetzner), which both computers can connect to, allwing me to access the other computer?