How can I delete rest of the line after a specific string?

Search mode regular expression, Find

=UUID:.*

Replace with nothing.

It's easy. Your question:

*://81.88.22.6/*=UUID:63969B2469B7A94EBBDBD7CB5B9C00BA
*://*-ad.cgi*=UUID:3C8EFF48B674CC42BF5B6E2B7BA820E7
*://*-ads/*=UUID:0D6CF7D5BE3F034C8A136CC99A074406

My answer:

[=].*

Result:

*://81.88.22.6/*
*://*-ad.cgi*
*://*-ads/*

Explanation:

= character, represent the character you want to remove
.* characters, represent all the characters after that

That's it.