I think the easiest (or, well, “the most direct”) way to solve this problem would be to use Google Tag Manager (GTM) rather than directly connecting Unbounce to Google Analytics (GA).
GTM allow you to quickly and easily load a variety of scripts (a multitude) into one “container” that you put into Unbounce as 1 script that covers all the pages you’d like to track things on (e.g., one container for one full domain, a group of subdomains, etc).
Each script in GTM is called a “tag” and each tag can be fired by one or more “triggers” that listen for various events that occur on your web pages. They can be as broad as “all pages” (for something like a GA pageview, or a Facebook Pixel page view) or as discrete as a click on one single button on one single page (for something like a form submit conversion).
To solve your particular problem:
In GA, what you would do is create a Goal for each different type of conversion - using a distinct “label” descriptor for each one (Contact Us, Trial Sign Up, etc.). It sounds like you might have those goals already.
GTM will allow you to create a “tag” for each of the different types of event you want - e.g., using the same category & action but a different label. Then, you can use individual “triggers” for each of those events.
All of your buttons have a distinct identifier, and that’s what you’ll set your “trigger” to listen for. Suppose you have an Unbounce landing page “example.com/get-some”. On that page you have a button for “Trial Sign Up” - and if you click on the button in your Unbounce editor, and scroll all the way down in the configuration panel, you’ll see it has a unique identifier along the lines of “#lp-pom-button-522”. Another button, say, for “Download E-Book,” would have a different, distinct identifer, e.g., “#lp-pom-button-544”.
What you would do is set up a trigger in GTM that tracks certain clicks, and set the trigger rule to be [click id equals #lp-pom-button-522] + [page url contains /get-some] and then you’d use that trigger to fire a GA Universal event “tag” that sends an event with appropriate category, action and label (“Trial Sign Up”) to GA. You would then set up a trigger for [click id equals #lp-pom-button-544] + [page url contains /get-some] for the tag that sends a similar event to GA, only with the label “E-Book Download” or whatever. Just make sure that the category, action and labels you set on those tags in GTM match exactly with the event criteria in your GA Goals, and you’re good to go!
You can read more about this here:
Install GTM > https://www.crazyegg.com/blog/easy-google-tag-manager/
Button Tracking > https://www.lovesdata.com/blog/google-tag-manager-button-click-tracking
Advanced > https://www.simoahava.com/analytics/track-form-engagement-with-google-tag-manager/