RustDesk

That being said, it's developed by Chinese and communication with them is tough. Some security issues still haven't been patched (no one actually knows why, they either don't reply why or reply in Chinese with a cryptic message like "why ask this" or something weird like that). They're also notoriusly against anyone speaking anything against them (I once commented on their subreddit that the devs are mostly Chinese, so communication is kinda difficult, after someone asked why they don't reply or give scarce replies regarding issues and PRs on their GH).

Still, it's free and open source, so you can give it a spin if you'd like. The servers that come by default are super slow, the idea is to make your own (which kinda beats the point of actually having some sort of a replacement for TeamViewer or AnyDesk... if I wanted to set up my own server, there are other open source alternatives), which drew me away from it from the start.

I still use AnyDesk with version 7.0.14 for Windows and version 6.0.1 for Linux. The older Windows versions because there is no red bar over the window that says "free version" or whatever and the older version for Linux because it just works better than the latest one (6.2.x), I have no idea why.