A lot of campsites here in France understandably close over winter months but even so there still remains a large number of puka municipales etc open to all-comers even if the prices are creeping up.
Maybe a bit off-topic but my experience is a fair number of municipal campsites (in France) have moved to private ownershipo by large chains). Or maybe just contracted operation, uncertain of details.
There seem to be some municipals still operating through Mairie but many seemed to be commercial chains. But prices were not massively different and facilities unchanged, everything pretty much the same except for the private company.
Internal operation I did notice at several was where operated by local authority different people would serve different functions at different times eg Acceuil still closed 12:00-14:00 (or later) but under private company at 12:00 the reception staff take the cleaning gear out and spend a few hours cleaning the toilet/shower block or get mowers out and cut unoccupied emplacements..,.
(I have a strong preference for municipal sites, generally much better (when all you want is a shower, toilet and somewhere to pitch your tent for the night).