Specifically, upgrading dhcpcd to version 5.6.0 complains that /usr/lib/systemd/system/dhcpcd@.service is already owned by package systemd-arch-units. Which package shall be the owner of this systemd service ?
Skrooge, a personal finances manager for the Plasma Desktop
dhcpcd should own it. You need the systemd-arch-units from [community-testing], which doesn't have it any more. (You should have both testing repos enabled if you use either of them.)