Even as delightful as Rick's audio tours are, they don't cover every possible city in Europe. Does anyone know of other sources for those cities he doesn't cover?
You should be able to find other options in the Google Play Store and the Apple equivalent.
I have looked for the same thing, because I love Rick's audio tours.
I considered "GPS My City" for a trip - I can't remember if it's an app or a website, but they had a variety of city tours with accompanying articles about the city. It seemed to be crowd-sourced content - that it, anyone who considered themselves an expert could submit an article and audio tour - and the articles, to me, didn't seem very high quality. I think I was able to download a sample tour, but I wound up not using any of them.
However, I went to Boston for the first time in 2019 and found an excellent, inexpensive walking tour just by googling for audio-guided walking tours in Boston. It wasn't part of a larger "walking tours all over the world" type site or app, it was Boston-specific.
Your best bet is probably google - search for audio tours specific to the city.
If you just google 'city audio guide walking tour' or something like that, you'll find a lot of options. When I do that, one that comes up is "City Walks World" which has tours all over the world to download They are 19.99, and a lot of the European tours have one or no reviews. You'll have to do some research and review reading, but you may be able to find what you're looking for that way.
Thank you for your helpful replies. If I find any wonderful sources for audio tours I'll let everyone know.