Running Big Sur 11.2.3 I've only noticed the mouse and typing lag on the monitor that i have rotated and scaled. And it seems to come and go.

I have the same problem with Big Sur 11.2.3. Not only mouse lags, the general framerate is low sometimes.

I'm seeing this with Big Sur 11.2.1 and I just downloaded DisplayLink 1.3 (I was on 1.1) I use a trackpad and the jumping is almost making the computer ignitable. Samsun Monitors and a StarTech to link the MacBook Pro to the monitors.

Lag sometimes affects typing speed also, not just the mouse.

I've noticed the mouse lag only occurs on one of my three monitors and correlates to the DisplayLinkUserAgent process going from using about 30-40% CPU to over 100% usage. The mouse cursor's movement is strobe like showing up in one place as I move the mouse and then disappearing for moment and then showing up somewhere else along the path of my movement often in a delayed/lagged manner to when I had moved it over a spot. This leads to shooting past where I want to click, or having to wait and check that it's where I want it to be when it finally shows up.

Adding tags to the comments to help others find this suggestion.
CPU usage, 11.0, 11.1, 1.1, 1.2, DisplayLinkUserAgent, DisplayLink Manager, Display Port, DP, USB, Lagged Monitor

I've been running qualitative tests and documenting in hopes of giving insight on this so they can support Bug Sur going forward. I've been updating my results here: https://displaylink.org/forum/showthread.php?p=91382