I got some Peter Storm waterproof walking shoes from Go Outdoors a few weeks back. They were on discount/member price at around £25.
I found them quite comfy to pedal and walk in. I’m just back from a gentle 5 days of riding in Holland with them as my main shoe (riding MTB flats on a well loaded gravel bike).
After 30 (overloaded) miles bashing headwinds along the Dutch coast back to the ferry on Friday I had no hot spots or foot ache and they kept out a fair amount of wind driven rain. They’re not light but I basically wore them the whole time.
I took my 5-10’s as my second shoes they never came out of the bag and they’re heavy.
I got some really cheap cloth deck shoe things from Sainsbury’s a couple of years back with a foam sole. Kind of thing I’d normally have to go car to beach. They would have been a better off the bike shoe. Very soft and very light and when they were new would have been perfectly acceptable in most non formal places.
The key thing for me on this trip (my first touring type trip since my teens a long while ago) was wanting a “back up” riding shoe as the Peter Storms were box fresh when I left and I wasn’t sure of their waterproof credentials. I wouldn’t bother with another pair of riding shoes again if I had those. If you don’t want to pedal in them or use less aggressive pedals then there’s loads of light (smart) trainer options with foam soles.