Settings → About shows the running version. If a newer GitHub release exists, that page prints the latest tag and the install command.
To update, run the same installer as the first install:
curl -fsSL https://terracotta4u.com/golem/install.sh | sh
That replaces ~/.local/bin/golem with the latest release (or set GOLEM_VERSION to pin a tag). Then restart golem serve.
golem version prints the binary version from the command line. Development builds do not report an update.