Not released
We tagged the tree for v1.38.0 but were not able to build a release. The tag point itself is fine, if you have pulled from this tag you should feel free to build and use the 1.38.0 binaries which result.
We applied a fix for our builder in 6c0e6a5, which is the only change between v1.38.0 and v1.38.1. Tailscale's released binaries are v1.38.1.