OK, as I thought I remembered, it is from the arch distro, Manjaro is an offshoot of arch,,
usually they are binary compatible, you have to enable the arch repository
Bear with me I did this 8 months ago, forget,,...
Open the gui, package manager, top bar, right, hamburg button ->preferences -> AUR ->enable AUR
The name will be downgrade, version #,,,, nothing else, not even capitalized
If you like scripts, it's just a clever bash script, plain text, you can look at it
usually they are binary compatible, you have to enable the arch repository
Bear with me I did this 8 months ago, forget,,...
Open the gui, package manager, top bar, right, hamburg button ->preferences -> AUR ->enable AUR
The name will be downgrade, version #,,,, nothing else, not even capitalized
If you like scripts, it's just a clever bash script, plain text, you can look at it