What signals can be sent to Google Business Profile or GMB listings to boost trust?

Make sure websites are optimized to increase trust.

Most of the prominence factors come through from the website. Have a well-optimized site, good title tags, pages for each service & location, main keywords on the home page.

Backlinks to the site also will play a factor.

Mentions and citations are also an excellent way to get the algorithm to ‘know’ that a business exists at a particular location. The more data the algorithm can accumulate about your NAP, the better.