I'm not sure if this is specifically what you're looking for, but some folks have developed software for the budget "Yi" cameras. It complements (doesn't replace) existing firmware, but you can bypass account creation and disable the manufacturer's cloud. I use mine only occasionally so I don't know how it stands up to frequent use.
There are different maintainers for different models, but as far as I can tell they're all pretty similar: https://github.com/search?q=yi%20hack&type=repositories
Edit to add they work pretty well with Home Assistant with this HACS integration: https://github.com/roleoroleo/yi-hack_ha_integration