HopToDesk is an open source remote desk system similar to AnyDesk and TeamViewer. However because it's FOSS, it does not nag or impede users who it thinks are using it in a commercial capacity and did not buy a license (AnyDesk has countless times put a 999 second wait on me with a nag screen just because it decided I'm using it commercially, and TeamViewer outright accuses me of using it commercially and blocks me from connecting and demand I pay for a license). There's even an option to set up your own C&C server if you're extremely security conscious.
Maybe better than RustDesk .
This page gives more alternatives to this app with specific criterias.
Maybe if someone makes a portable version of such a software as a beta test, or eventually adding it to the official list, to fill the gap & to compete Teamviewer. Maybe.. But behing the scenes, hides another story.
'Life is a strategy game, where roles are already distributed'
― Neo Buddha ―