There is a well documented opensource alternative to Tailscale - Headscale. The tailscale client is already opensource, Headscale is opensource drop in replacement for the control server which isn't, and fully compatible with Tailscale clients:
If you can be bothered running the headscale container, you generally don't need to pay for tailscale. It's been pretty well supported and widely used for a number of years at this point. Tailscale even permit their own engineers to contribute to headscale, as the company sees it as complimentary to the commercial offering.
https://github.com/juanfont/headscale
If you can be bothered running the headscale container, you generally don't need to pay for tailscale. It's been pretty well supported and widely used for a number of years at this point. Tailscale even permit their own engineers to contribute to headscale, as the company sees it as complimentary to the commercial offering.