It won't work because Add/Remove Programs (Also called pamac) depends on libalpm (version 12) which has a newer release, but pamac has not caught up with changes in the new release yet (the command line tool pacman has caught up with the newer version of libalpm and has no problems).
So to install stuff, you can either use paru or pacman on the command line, or use a graphical application called bauh (command to install:
paru -S bauh --skipreview
). Any other solution which claims to get Add Remove Programs (also called pamac) working does so by downgrading libalpm pacman (the downgraded version comes with an older version of libalpm). This will take away the parallel downloads feature 
.
Edit: Edited to clarify that the package downgrade is for pacman. Thanks @jonathon