very slow to plot under linux (ubuntu 16.04 and 19.10) but fine under manjaro (arch-based)

[Marc Rain]

For those who have tried to run Stata in Linux, probably already encountered some issues related to the icons and libpng12 library... while those got fixed and Stata starts normally and display the icons since stata15.1 I think, somehow in Ubuntu, Stata takes really long (15 to 20 seconds on a i5 5th generation) to plot a scatter plto [twoway scatter x y] with some 150.000 observations

• plotting works fine under manjaro (arch-based, with gnome 3.34.1). same script takes only 1 to 2 seconds to plot, just as fast as in windows.
• I also tried multiple releases of Stata (mp, se) and also multiple versions (14.2, 15, 15.1)... and the results are the same across all versions: works as expected in Manjaro but veeery slow in Ubuntu.
• other than plotting, Stata seems to run just as fast as in other systems.
• i first thought the issue was related to the libpng12 library. I installed this library in several ways and several versions, including using the binary from arch repository, from this ppa as in this tutorial and also manually from xenial's repo.
• also tried in elementaryOS (5.1) and ubuntu 16.04, so it is not a problem only with the 19.10 version.
• a "line" version of the same plot [twoway line x y] plots quickly.

my best guess so far is between the libpng12 library (which is not properly supported in newer versions of ubuntu) and its dependency zlib. (in ubuntu: zlib1g) maybe someone around here already have and solved this issue... anyone?
(I am aware of the tips for speeding up plotting, such as collapsing the dataset or dropping