I generally prefer vanilla OpwnWRT or maaaaaaybe one of the nicer Tomato forks.

There's a Hong Kong company called GL-iNet which makes routers whose OEM firmware is just OpenWRT plus their own web interface, but they actually also have the stock one from upstream pre-installed as well.

I've bought routers from them for years. I usually make sure that they're fully supported in a stable upstream release of OpenWRT, then replace the firmware with vanilla, which is no fuss. Then they continue to get firmware upgrades for many years.

DD-WRT I think of as a messy thing for backporting as many features as possible to routers that are locked to old kernels because they rely on super proprietary radio firmware blobs.

Take a look at GL-iNet, the WRT routers from Linksys, and the OpnWRT One or whatever it was, and try to figure out where you might fit in that landscape. Maybe you can support some features they don't, maybe you can take a radical upstream-first approach to appeal to free software enthusiasts, or maybe you can market to Americans who want manufacturer based in their own country. But those are antecedents who may also be your competitors, so it's with seeing what they're doing.