Tailscale keeps the private keys locally, . It just facillitates setting up wireguard. They could steal your private keys, as could any program you install with root access. But it would comepletely destroy their business, and it’s open source. I really dont think they have anything to gain by tricking everyone
Where’s the source code? Seriously, the only thing I can find for drive & calander are repos that were archived in 2021