Need help doing a Lookup with a calculated string


I use a formula to extract the base domain from a long URL


which will take something like:


and return the base domain:


I then want to use that base domain to do a lookup into a table that maps the domain to an actual human readable title of the site, but the Lookup won’t let me use the extracted URL. The formula field where the string manipulation occurs is not offered as one of the options for Lookup.