Palm Desktop for Mac

The last ever version of Palm Desktop for Mac [4.2.2] was released in 2008 - though 4.2.1 is more common, & still available if you look around - https://palm-desktop.en.softonic.com/palm though I haven't run the Mac version in a long time, so compatibility might be suspect.

I've found it's simpler to use a VM of Windows 7 & install to that - though my Palm iQue 360 installer now fails on anything other than a backup restored drive, as the associated internet app downloader points to nowhere.

It's not hugely surprising that software for something that hasn't been manufactured in 8 or so years is not easy to obtain or run.

[download locations untested]

Late answer, but I personally use Sync Buddy on my current Macs running Mojave. It doesn’t replace Palm Desktop but is perfect to install apps, get data and retrieve data.