Sailfish OS on a Sony Xperia XA2 - Tweaking & Customisation
This article has a parent article.
Disable High Volume Warning
Disclaimer: be aware that doing this you remove a safety feature and could damage your hearing. Use at your own risk.
It's the same idiotic warning one gets on Android phones when one plugs in headphones and starts raising the volume.
To completely disable it, edit
/etc/pulse/mainvolume-listening-time-notifier.conf (also see "SSH" and "Becoming root" from the main article). Replace
mode-list = lineout,hs
#mode-list = lineout,hs mode-list =
Save & exit: Ctrl-x, answer yes.
There's a patch for Patchmanager 2 that modifies the UI instead of the pulseaudio daemon. Looking inside the package, it only changes one line in one file, I guess it could be applied manually too. Not tested.