Ultra simple website to tell people a service is down
npm run start
Using Cloudflare
If you want to use Cloudflare to handle redirection to the website, you can use Page Rules.
First, make sure the DNS records for the (sub-) domains you want to redirect are being proxied through Cloudflare. Then, head over to Redirect Rules (Page Rules are harder to configure, and it seems like Cloudflare itself is more keen of Redirect Rules too).
Create a Single Redirect rule that looks similar to:
# When incoming requests match...
(http.host in {"example.com" "another.example.com"})
# Then URL redirect
Dynamic
concat("https://your.host.tdl/?destination=", http.request.full_uri)
302
Enable the rule and everything should be set!