PCSX-R in Ubuntu MATE 18.04 cannot configure controllers when more than 1 gamepad connected

On Ubuntu MATE 18.04 (both 32 and 64 bit) I can't configure controllers in PCSX-R (package pcsxr from the official repositories) when more then 1 USB game controller (standard USB HID device) is connected to the PC.

There's just nothing happen when "Configuration" => "Controllers" is clicked in PCSX-R if there is more then 1 game controller connected to the PC.

When only 1 game controller is connected then it's fine and the configuration screen will show up.

Older Ubuntu MATE 16.04 don't have this problem.

Also: on 16.04 the configure-screen shows the controller manufacture/model in the list, in 18.04 it only shows "1: null" when one controller is connected. More controllers connected = the configure-screen can't even get opened.

It looks like the problem lies in the newer input-plugin (1.2.0) which is delivered with the pcsxr package in 18.04. In older 16.04 pcsxr package the plugin is version 1.1.0.

A dirty "solution" to get it to work at this moment is to copy the old plugin files from Ubuntu 16.04 to 18.04:

Overwrite "cfgDFInput" and "libDFInput.so" in "/usr/lib/i386-linux-gnu/psemu" on 18.04 with the older files from 16.04.

Take /usr/share/psemu/dfinput.glade2 from 16.04 and put it in the same location on 18.04. Then install libglade2-0 package and the pcsxr in 18.04 will work with 2 or more USB gamepads connected using the older 1.1.0 input plugin.

But this is not a long-term "solution". At a next update the replaced files will get overwritten.

What would be a good solution to this problem?

This bug still exist in Ubuntu MATE 20.04 LTS and it's still fixable with the files from 16.04 LTS.

Why is this never fixed?