@eht16 @techee Look at the PKGBUILD of mingw-w64-libtiff:
https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-libtiff/PKGBUI...
You don't have to resolve the conflicts between the two libstdc++ libraries. You only have to build your own libtiff.
This is how I configure it:
./configure --prefix=$HOME/tiff --disable-static --enable-shared --disable-cxx --disable-jbig --disable-lerc --disable-libdeflate --disable-lzma --disable-zstd --disable-webp
The resulted $HOME/tiff/libtiff-6.dll is very small. The only dependency is libjpeg-8.dll.
Note: I'm using MSYS2 UCRT64.
After adding libjpeg-8.dll from MSYS2 UCRT64 and my own libtiff-6.dll, Geany runs just fine.
You don't have to go as minimal as me. You only need --disable-lerc, this will enough to get rid of the annoying libstdc++ issue.