Surface Pro X and Surface DUO, and yes, the Pro X is driving two 4K monitors, the new keyboard and mouse is the MS Designer Mobile and MS Mobile Mouse...the little guy on the desk is Vector (Cloud AI Driven Companion Robot)
I have an LG 34WN80C-B 34 inch WQHD monitor, I'm using USB-C (which also deliver power and USB Hub). Works as expected. Does your model support USB-C to USB-C?
The other option is using an active USB-C to HDMI cable.
Are attaching directly or through a dock/hub? It could be the cable or anything in between the Monitor and Device.
Also, make sure all the updates are complete. While plugged into the monitor do a hard reboot and see if it reports correctly.
I'm the wrong person to ask, as I upgrade with every new generation :) the 11th GEN will be much better in graphics performance and should get better battery life...
Some of the Docks use the DisplayLink Virtual GPU (actually it uses the CPU/GPU combo to render) but the Thunderbolt or True USB-C uses the onboard Graphics...
Microsoft released a Surface Connect to USB-C adapter, but it is unavailable. Is the Dell Dock in question Thunderbolt? If, yes is it backwards compatible to USB-C?
Buy Surface Connect to USB-C Adapter - Microsoft Store
It fits into my work life; the updates have been good from the OS/Launcher, but the Edge and Teams updates have caused regression with running expanded across both screens.
Teams for a short time allowed nine video feeds and now it's back to four, and Edge only supports gesture navigation
If you are willing to use it vertically there is a solution (ish)
Vertical Docks | Vertical Docks
Amazon.com: Vertical Dock for MS Surface | Dock Your Surface up Next to a Desktop Monitor (Surface Pro 7 / Pro 6 / Pro 2017 / Pro 4, Basic + | with Landscape kit, Without Electronics, Without...
If you run on a maximum power while plugged in, driving a 4KUWHD Monitor with multiple decks, spreadsheets, Outlook, Edge multiple tabs, OneNote and doing a Video Conference Call I've over-heated the Pro X :D
The Pro X can get warm occasionally, and like any device you can push it beyond its thermal capacity, but under normal productivity and note taking you should be fine...