U3219Q, daisy chain to U2515H?

That will not work. The first monitor in a daisy chain must have a DisplayPort (DP) MST out port. The U3219Q only has a DP in port.

In theory...

Surface Pro 7 USB Type-C out port --> USB Type-C to DP cable --> U2515H DP in port (Menu- Display- DP 1.2 Enable)

U2515H DP out port --> DP to DP cable --> U3219Q DP in port

U2515H User's Guide page 26 =

@Tone123  In addition to the fact that the U3219Q doesn't have a DisplayPort output, if you wanted USB 3.x data to run over your USB-C connection to use USB 3.x with the U3219Q's built-in USB ports, you wouldn't have enough video bandwidth to run 4K 60 Hz + QHD 60 Hz.  So you'd have to sacrifice resolution and/or refresh rate on one or both of the displays in the daisy chain.  If you were ok with only USB 2.0, you would have enough bandwidth from that particular system because it supports the current DisplayPort 1.4/HBR3 over USB-C standard, but that's still relatively rare today.  With most systems that only support DP 1.2/HBR2, they could run only a single 4K 60 Hz display when using just USB 2.0, or only a 4K 30 Hz display when also running USB 3.x.  That's all probably WHY the U3219Q doesn't include a DP output for MST.  But it's also why you shouldn't try to set up a daisy chain with the U3219Q at the end of the chain and some other display that DOES have a DP output at the beginning.