You are using the lowest end, lowest of powered, 8 year old Macās. There is nothing ālatelyā going on here.
Itās got Intel Graphics, and was the last machine Apple released that wasnāt considered āproā or āairā
It was never more than 2 cores at base clock of 1.4 ghz at the highest configuration.
It is officially classified as a vintage machine one.
With that said, it technically can support 4K@60 in the ideal configuration. But understand also that it probably canāt support a HUB. IT DOES NOT HAVE THUNDERBOLT.
it has usb 3.1 gen 1, and ONE port.
So either DP alt mode with PD, OR a Hub, unless you are willing to spend the cash on a hub that can multiplex it all.
None of this is an Apple issue, itās the tech of 8 years ago, combined with your reluctance to buy a hub made by engineers.