3. Can your Code be mixed with Libraries like Botan or is it too much "UPP-specific"?
No reason not too.
Quote:
4. Can I use self-compiled Version of ICU, OpenSSL/Botan, SQLite etc.?
Sure.
Quote:
5. If someone knows this: I saw that you switched to a specific Clang Variant. Can I use the MinGW-w64 Compiler on MSYS2 as well?
Yes, with some effort. The clang we are using about as good as you can get in Win32. Anyway GCC is still supported, but you will need to configure it yourself.
Quote:
6. I remember that in 2018, when I tried to compile against MinGW, somehow always VC++ Flags got added and compilation always failed. It was the main reason I stopped playing around with UPP. Has this been fixed? I am talking about self created Configuration Files.
I do not remember it being broken. Most likely you had wrongly configured build method (probably wrong builder).