Do I understand it correctly that all versions will then produce values like my current Windows version? It is good that the values don't differ, but for me the files generated with my current Linux version, which is linked against libsndfile, worked well with the programs I use and the files from the Windows version were too quiet. Wouldn't it be desirable to bring the current Linux (+libsndfile) behavior to the (Windows) versions without libsndfile?
You were right, unsupported audio format error for my Windows version and no problems with my Linux version.
The sample format is float32. I don't know whether the executables are linked against libsndfile and I honestly don't even know how to find out. For windows I got the LAME 3.100 64bit package from RareWares. It seems to only contain the lame_enc.dll. On Linux I got it via apt.
ReplayGain values on Windows and Linux differ