Open core can work, but you really have to find very strong product market fit on the proprietary side--ideally with features that discriminate between users who are relatively happy to pay and users who are not. (There's a reason "SSO tax" is so common.)

And you really have to believe in open source and have the discipline to keep investing in it, otherwise the temptation is ever present to throw more and more effort and resources into the proprietary parts.