How do I go about finding out what Google search?
A few indirect ideas I've had are:
* Look at Stack Overflow questions with the highest number of views * Look at GitHub issues with the highest number of engagement
SEMRush has a free version where you get ~10 queries per day, so you can explore search volume for terms like "test automation software" and drill down from there. It won't 100% match GKP, but will be similar enough in magnitude.
If you're comfortable using APIs, https://dataforseo.com/ is going to be the cheapest/easiest route. I've used it for past projects, and it is basically like $0.10 (don't quote me, but around there) to fetch monthly search volume for <700 terms per batch. I think they can also provide search suggestions, estimated CPCs/competition indexes and other metrics as provided by Google.
Google Trends is easy/simple, but only gives an index score-- not actual query volume. Lots of marketing people use this for ideation.