for linux you can use xterm, or for windows you can use the built in RDP or a 3rd party such as my commented remote administrator; there are countless how-to's on remote desktop protocol stuff out there.... TV is just nice because they have a 3rd party reporting/relay server.
I tried different services and applications, but most of all I personally like TeamViewer. I think this is the most successful, stable and reliable solution for organizing a remote desktop.
teamviewer is paid program (and way too expensive imo)
you can cheese it, but it will notice you using it for professional purpose and kick u off eventually
what a headache
i use:
https://remotedesktopmanager.com/home/download (basic RDP connection no port stuff needed)
free, easy, no license shit
people using teamviewer in 2019 :O
Don't have many rigs to monitor so Teamviewer still works. I did get kicked out by them after I used my TV account to help out a friend setting up his rigs... But a couple of emails to their support and all was good and the free account was re-activated.
If you do scale though, you'll certainly get done. And yeah, there would be cheaper alternatives out there.