While AUR packages generally show up on pamac, there is a specific one which does not.
When I look for “gramps” on pamac, I only get to see the community package which is slightly outdated. I cannot figure out why the AUR package mentioned above is not listed.
As aforementioned, different AUR packages (nheko etc.) happily show up.
The package you’re linking to is not in the AUR, it’s in the Arch repositories (take a closer look at the URL).
If the one in the Manjaro repositories is outdated, you’ll have to wait until the newer version reaches the Manjaro branch you’re on.
testing is ok, ok in stable in some days