Hello Experts,
Different playback volumes with identical audio settings in different versions of Audacity. I use a Dell notebook Vostro 5510 Wintel platform with Realtek Audio and Win10 Pro latest updates.
My Audacity Portable 3.2.1 gives a very loud playback appropriate to the recording (Windows Volume 87 Audacity is set in the mixer = SystemVolume) of an audio file with vocabulary training that I saved as ogg in 2020. This is also how VLC and other players play it.
With Audacity Portable 3.1.3 playback, playback is quiet, as if I had the volume turned down to 25.
With Audacity 3.5.1 installed on the notebook in Windows, loaded and played, the playback is very quiet, as if I had turned the volume down to 5. See the screenshot…
The same file!!! always loaded with Windows WASAPI as host, speaker selection headphones, Audacity output level is always the same up to approx. -6 in all 3 versions. Mic is set to speaker Realtek audio loopback, 2 (stereo) recording channels.
The same behavior on the new notebook Vostro 5630 Windows 11 Pro, only version 3.2.1 plays the audio file at the “correct” volume.
Now you come 
I would be happy to continue here…