Unfortunately these evil tech businesses have very little official avenues to reach them. Usually it's either through public outcry, or through the official form you see in error logs, which requires creating a google account if i remember well.

Arguably, if you're operating a business and have a client using Gmail, you could have you and your client contact Google support to ask allowlisting, then sue Google for anti-competitive (monopolist) behavior if they don't comply. I don't know of a case like this, but it should be an easy win and would set an interesting precedent.

I'm personally not into legal stuff, but if some startup people around here with a few lawyers would try this approach... :)