I suppose it's open core. Open Source is hard because you have to separate people from their money even though the code is "free." I'm not saying it's _the_ answer, but browserless.io isn't VC backed, and it certainly makes more money than most of the Patreon/sponsor models. I understand that it's not just a library, but a full-blown service, which makes it easier to market and sell.
Have you considered a hosted product? I have no idea what your audience is like, but that seems to be where we've had a lot of success. Happy to chat anytime as well: joel at browserless dot io.
OpenFaaS has been a struggle even since it was started, even with a large community and many commercial end-users, none pay for support, services or sponsor.
Most of the time saying that Open Source isn't sustainable results in some smarty dropping Elastic or some other massive VC-backed company in like GitLab. It's not helpful.