Time to start showing the prototype! We implemented both client and vendor pages, hooked up everything to Stripe with the debug key and validated everything works on desktop and mobile (including crummy old phones).
And people hate it - a reactive web site seemed a good 'one size fits all' solution for all platforms, but the progressive web app works oddly on some phones, and parts of the screen appear and disappear as the phones get rotated around.
Switching gears and going back to just plain old apps on mobile. Rather than do in Kotlin, we started up in Flutter since the new release looks really good.