> When I asked an AI how I would go about judging interest, building, raising funds, and manufacturing, it seems doable but expensive

Just a thought: make a small business out of setting up people's home networks and small business networks. The cost is negligible, you will learn about unmet demand, and you will be able to reach people who aren't technical in the process. It will cost you some money, in the sense that your service fees would almost certainly be less than your day job. On the other hand, potential customers would be paying you for market research and product development. In some respects, the market research will be more valuable in the sense that you are working with potential customers.

I say potential customers because selling a kit will reach different people. On the otherhand, it will tell you what has to go into that kit. For example: I doubt that flashing DD-WRT to existing hardware will suffice. There will be some people interested in that (someone else does the research, fear of bricking), but would those people commit to buying and setting up your product? Throw in a setup wizard that makes setting up ad blocking, VPN, or anything else that major vendors don't have much interest in simplifying, and you will likely have more success.