XPS 8940 integrated HDMI problems with boot, wake from sleep, and video corruption

i5-11400 XPS 8940 system. Brand new monitor (Samsung M7 43") plugged into built in HDMI port with a cable that came with the monitor. Discreet video card is unplugged. Dell has just replaced the motherboard and it did not seem to help. There are 3 issues.  

1) On fresh boot I experience the problem described at Solved: XPS 8940, onboard HDMI activated only after 5-10 minutes - Dell Community - the machine spends several minutes without keyboard lights on, mouse sensor blinking, the monitor turns on once in a while but never displays anything.  In 3-5 minutes it gets to Win 11 login screen and everything works.

2) When waking up from sleep I experience the problem described at M7 32 Smart Monitor will not wake from Sleep/Stand... - Samsung Community - 2196458 - monitor does not wake up from sleep and needs to be turned on manually.

3) After a bit of use, typically in Chrome and a bit less in Edge, the display gets corrupted with pixely, multicolor lines. Display turns off if I hover over the offending tab(s) and comes back if I move off it.  Sometimes closing the app fixes the issue for a bit, sometimes a full restart is needed. 

The first two issues do not occur with my old monitor (Dell u2412m plugged in with HDMI-DVI cable).  They do not occur if I use discreet video instead. And they do not occur if I plug the new monitor into the old computer (Vostro 470).

The third issue occurs with both monitors. It also occurs with my Dell u2412m plugged in with DP-DP cable. It does not occur on the old computer.  I suspect it does not occur when using the video card, but I have not tested it long enough that way to be sure.

I just updated to the latest UHD 730 driver available directly from intel to see if it will help with the third problem; will update.  The Dell recommended driver is almost a year old at this point and since the motherboard swap didn't fix it, a driver issue seems likely.

I have all updates installed as of yesterday including the just released bios.  Hardware has been checked with diagnostics and, in any case, just came back from Dell's repair center.

Any ideas?