tailscale-app requires a kernel extension to work.
If the installation fails, retry after you enable it in:
System Settings → Privacy & Security
For more information, refer to vendor documentation or this Apple Technical Note:
https://developer.apple.com/library/content/technotes/tn2459/_index.html
Installing tailscale-app means you have AGREED to the license at:
https://tailscale.com/terms
