Cannot create forks. No namespace to select

Summary

I'm not able to create forks. No options appear in the required namespace field

Steps to reproduce

1. Click the button to create a new fork of a project, e.g.: https://gitlab.com/gitlab-org/gitlab/-/forks/new
2. Try to select a namespace

Example Project

https://gitlab.com/gitlab-org/gitlab/-/forks/new

What is the current bug behavior?

No namespaces appear

What is the expected correct behavior?

Valid namespaces listed, including the current user's namespace.

Relevant logs and/or screenshots

The browser console shows:

new.json:1 Failed to load resource: the server responded with a status of 500 ()
createError.js:16 Uncaught (in promise) Error: Request failed with status code 500
    at t.exports (createError.js:16)
    at t.exports (settle.js:17)
    at XMLHttpRequest.p.onreadystatechange (xhr.js:69)
    at XMLHttpRequest.r (helpers.js:72)
t.exports @ createError.js:16
t.exports @ settle.js:17
p.onreadystatechange @ xhr.js:69
r @ helpers.js:72

Kibana logs show Rack::Timeout::RequestTimeoutException (internal)

Output of checks

This bug happens on GitLab.com