I intend to start cataloguing my private library (approx. 200-300 books) as long as it is still relatively small; what I don't want is to end up with a proprietary file or database format that ties me to a single app or vendor. I'm indifferent towards whether my library catalogue remains purely private or forms part of a world-wide federated catalogue. I imagine there must be some FOSS or open initiative for bibliophiles (like there is for geo data with OpenStreetMap).
My search so far turned up OCLC/WorldCat (but I haven't figured out yet if they only catalogue public libraries, or also encourage private book collectors to contribute)
Is there some established / incumbent solution for cataloguing a private library (for people who favour the FOSS idea)?
Clarification: This question is concerned with physical books - not eBooks. Many of the books are antiquarian, predating the introduction of ISBN.
I'm looking for a solution completely free of charge. The catalogue software platform can be either an Android device, or a modern web browser, or a Windows 10 desktop.