"Evangelism goal is to convert listeners into new supporters / enthusiasts."

And they buy things. But I agree that marketing would be a better term in many cases.

I evangelize the concepts of open source and avoiding giving up your data. Meaning any time I think it's topical and not annoying, I spout the opinions and the reasons for them.

As far as I can tell I have no "buy things" motivation. I am not trying to get my sister in law to hire me to install and maintain an asterisk phone system or an instance of nextcloud or add a custom feature to vlc etc. Nor do I do those things in general where I would benefit indirectly if more people wanted those services generally.

There's a difference between someone who genuinely believes what they are evangelizing, and paying marketing people to spread some corporate opinion.

The OP is referring to the second type I think.

Of course the two are not mutually exclusive, you could have an evangelist job for an open source company selling data protection software/services for example.

Its the same things, they are just selling the concept and the product, not just the product.