You’ll need to use | float(0) in templates. All state values and attributes start out as strings. Also setting a default value in the float(#) cast will ensure templates don’t break when the value is invalid.

That means use this style: {{ state\_attr("light.kitchen\_sink\_ceiling", "brightness") | float(0) }}

We need more information to recommend anything. Do you need high voltage switching? Do you have zigbee, zwave, or only wifi available? How much integration or local on device control do you actually want or need?

Right now - easy, with the difficulty going up over time as the main Chromium codebase continues to change (and especially as it gets security updates). I think I’ve read that some variants (Brave?) have committed to supporting ManifestV2 for as long as possible, for instance with their own fork.