Elastic [1] and Gitlab [2] both operate with a similar model of offering free, open source versions of their software with additional paid-for enterprise features.
Don’t get me wrong, sometimes it can get hate or complaints from the community, but at the end of the day, a lot of amazing open source software wouldn’t be available today if they weren’t able to be monetized in some way.
A lot of times, open source software wouldn’t be able to get actively developed, be able to afford security audits, quickly patch bugs, etc. without a paid person/group working on it, and there’s nothing wrong with that.
It is up to you, however, to decide how you’d like to raise funds. Some projects (iRedMail) provide a “Pro” version, others offer advanced support/installation (Canonical), and even others just look for donations. If you’re curious about how to proceed, I recommend checking out https://opencollective.com/discover for great examples.