install a new xubuntu 20.04, move your stuff to it.
Now you realize the taskbar is a lot crappier than years ago, its extra slow. And going over all GUI accessible options and messing with them does not help. But google will eventually lead you to a .config/gtk-3.0/gtk.css and XfcePanelWindow-popup-delay amongth others. So you copy and paste the example and change the popup delay to 0 or 1 millisecond. Who on earth would intentionally want a GUI to react with delay ?
Now the panel appears quicker but it still doesnt disappear. Theres a autohide feature with 3 settings none really work and 2 opacity sliders, if one sets autohide to always and “leave” opacity to 0 it disappears quickly.
After about 10 minutes of attempted use the panel drives you nuts by behaving in a hard to describe manner, it sometimes appears when you move the mouse to the edge (as it should) sometimes when the mouse just gets close (which is fun when there is something in that area other than the panel you want to click on) but is still far away from the edge. Again going over all GUI options and all text file options known, you find XfcePanelWindow-autohide-size but it doesnt make things better. And then suddenly you realize what is happening. You set opacity to 0%, so you change that to make it vissible, and here you realize the panel auto hides with a random delay (which you didnt see as it was quickly switching to transparent).
Finally? you change XfcePanelWindow-popdown-delay to 0 and think all is well but after another 5min of attempted use you realize the panel is still alot slower than it was years ago and on slower hardware, its also eating alot of CPU.
Setting all opacities to 100% and making sure no fancy effects are turned on (no none where on). Finally the panel is ok and you cant tell anymore if its as it was previously. Sure you could write code that renders that panel many thousands of times before it appears but you didnt write it and also dont have the time ATM and whoever wrote it had different priorities apparently … But you make a note on your todo “try/test window managers” but then again xfce works well enough so maybe you wont …