This was not working for me in macOS.
So I just followed what's done in other libraries (like gcrypt or chickadee) where there's no Guile 3 version check. It now works fine with Guile 3.0.4 in macOS.
I'm wondering why this was added in the first place.
You're right that the .so.1 extension is not strictly needed. I added it because (1) it clarifies which SONAME we're targeting, and (2) many distros ship .so as part of their -devel packages whereas .so.N is part of the regular package.
So my choice would be to keep it, except on macOS. We can do that by checking %host-type.
Sounds good. Just made a change. Note sure if that's what you had in mind. We are now specific as well with the dylib file name.
Applied, thank you!