I also see some KF5/Plasma5 stuff mentioned in there. Arch (and therefore Garuda) moved on to KF6/Plasma6 a while ago.
Example: The khotkeys no longer exist in Arch. So remove that and it's unneeded dependencies and try updating again.
Pyside2 is an AUR package, so try removing it first, update the system, then install/build it again if you need it.
Anything in the AUR is not important for Arch to function. Only to other AUR packages.
Any caldav web app should be able to do it.
Any reason it needs to be a webapp and not a native app for your OS?