EmbasyOS has a policy of not packaging proprietary software. The core of tailscale is open source but the control server and gui clients are not.
Embasy could add headscale, but have not done so yet.
They are working on a different solution which is "going to be towards the end of the year at soonest unfortunately."
They suggest using "a VPS as a dumb proxy for all your connections." adding "this will be made fairly simple in the coming months, and you will see guides popping up for setup." though I can't find any guides.