Good remote desktop programs

[j7n]

What is a reliable, performant remote desktop software today, which doesn't have any interations with Windows, and can run on a variety of older Windows versions? I would like to be able to access my computer remotely on a guest computer where I may not make any configuration changes. The server would run on Server 2008 R2 x64 that is somewhat weak, and the client would likely run on Windows 10 and 11. The client should be portable. The server should not do heavy-handed security or compression. The available bandwidth is 60-100 Mbit/s.

I could open a (secret) port for Windows Remote Desktop which is fast, but I am afraid that it would refuse to run on new Windows for this or that reason, as is often the case. I wouldn't be able to confirm any logins on the server or tweak it.