I have figured out a way to stably upgrade to Xfce 4.14 in a test Workstation 15:
Five steps (I recommend only to try this in a disposable test VM):
echo -e "deb http://download.opensuse.org/repositories/home:/stevenpusser:/xfce-4.14/Debian_10/ /" | sudo tee /etc/apt/sources.list.d/home:stevenpusser.list
wget -nv https://build.opensuse.org/projects/home:stevenpusser:xfce-4.14/public_key -O Release.key
sudo apt-key add - < Release.key
sudo apt update
sudo apt full-upgrade
Results of testing Xfce 4.14:
Things I notice it fixes / improves:
HiDPI, once and for all. (Appearance > Settings tab > Window Scaling to 2x, and then Window Manager > Style tab select a hdpi / xhdpi theme for the buttons.) This makes it much sharper text rendering for modern HiDPI monitors. It looks ‘clear’ where the current Xfce is ‘fuzzy’. It completely resolves Whonix 15 is blurry compared to Whonix 14?.
Small thing: Taskbar (‘panel’) items are finally non-dim and easier to read. Been a small bug for years.
Things it sadly doesn’t fix that I thought it might:
There may be other improvements reported by the Xfce community, but I won’t spend time searching out for what they may be. I’m welcome to hear of any.
This changelog indicates possible video driver fixes (e.g. for video playback within Whonix), I have not tested yet.
Conclusion: it’s not the spectacular improvement I thought it’d be. However, for me it’s worth it alone for the HiDPI support.
So @Patrick, I understand if you don’t consider HiDPI support alone being worth implementing Xfce 4.14 into current Whonix packages (by emulating what the above isolated repo does). It does seem stable however, no issues noticed, I only needed to reboot the desktop environment after upgrading.
So that’s my report.
I may have more thing to report over time, e.g. I may test out video driver and video playback support. My recommendation to not wait another 2 years for Xfce 4.14 for the Whonix community may strengthen.