Hey. ARD works great on a local network, but is not built for use over the internet. Most local tools like ARD would need specific network/router/firewall configurations on the network where the remote device is, which may not be allowed or supported.
Generally speaking...the easiest-to-use tools have an agent or client that gets installed on the device you want to connect to, which talks to a server. This outbound connection allows the agent to initiate a secure connection without any tweaks or changes to firewalls or routers, which is the secret sauce to easy connections over the internet.
You could try using the built-in functionality with Facetime (
Instructions here). Take a look at some other options in this write up too, which also lists
Facetime.
Google Chrome has a free browser extension too...I used it years ago and it was OK, but updates broke it frequently, so one needed a savvy user on both sides to keep it happy. No idea if it is still is so fiddly.
If you want really simple, reliable remote connection, you might consider a paid tool. There are tons out there. GoTo was always good, but not cheap (monthly cost).
Teamviewer has a free version for personal use, which may be the most popular free tool out there.
Here is a list of more to investigate too.
