v1.0.0
For Windows (x64):
Download MPDCtrlX.1.0.0.Win-x64.zip
Unzip it, look for "MPDCtrlX.exe" and run it.
(You may get a warning dialog from Windows's defender when launching the exe because the exe is not digitally signed. I generally do not recommend installing/running any random app from the internet. However, if you know what you are doing, you can just click "More info" and proceed to run it. )
Also, check out the new (and original) MPDCtrl v4 which is available at Microsoft store.
For Linux (x64 Debian/Ubuntu):
Download MPDCtrlX_1.0.0_amd64.deb
Install and Run
~$ sudo apt install ./MPDCtrlX_1.0.0_amd64.deb
...
~$ MPDCtrlX
Note: You might need to click the black triangle next to the word "Assets" below to see what you are looking for.