I vaguely remember some issues with extensions in ungoogled chromium. Maybe I should give it another shot.

Depends on what you mean by “private”. I would not trust it much, but it’s not a bad Chromium based browser when you need one. Use something like LibreWolf for much more privacy out of the box.

An outdoor WiFi access point would help with garden coverage

I believe most people who care about privacy don’t trust Gemini or Google in general. So it’s not an issue if you already not using Gemini app. It can be uninstalled (at least for now) even without going alternative ROM way