Rustdesk is an open source alternative. You can run your own server if you want, or use theirs for free.
DWService.net, is also open source. They take donations too. This one gives the remote user admin access to the machine, so more for tech support/MSP use, not so much one you'd setup for users.
Lite Manager is a commercial product, with a pro and free option, and competitive non-subscription pricing. Available for Windows, Android, Linux, etc.
