FWIW, most of the TypeScript lines of code are in the E2E tests[0] and the webapp dir [1], which, as the name suggests, contains "the client code for the Mattermost web app". So we should really only be counting lines of Go code.
[0] https://github.com/mattermost/mattermost/tree/master/e2e-tes...
[1] https://github.com/mattermost/mattermost/tree/master/webapp