It seems that recent Macbooks M1 have this issue. Some users reported fixing it using a USB-C to DisplayPort cable.
I did not have that issue when using the HUB @30HZ, but the mouse pointer was lagging, sometimes it didn't "flow" at all. Now it doesn't do that, but if I get up from the computer and it goes in stand-by... God forbid!
I would return the Macbook Air if I hadn't bought it on the other side of the world. Little did I imagine the pain that it would be to attach it to an external monitor.
Having to deal with the cable rating, the different ports etc. is a PAIN.
I want to be a bobo user, not a tech savvy one. I no longer have the time to research for hours on cables, monitors and tech spec.
I should have stayed with my old 2002 MacBook Pro. 15" was great even on the move, had no issue when connecting to an external monitor, also because it was HDMI to HDMI. Apparently, LG claims that when a video format conversion is involved (which is the case with newer Apple models that only have a USB-C ports), they no longer guarantee the same performances.
This is all very frustrating.
I was going to mention this, but didn't want to ruin your day.
A video signal over USB is never going to cut it, over HDMI or Display Port. The device needs either VGA, HDMI or DP out, end of story.
The mouse will lag because the refresh rate from the device to the monitor is too low.
My MacBook Air only has two USB-C ports.
Looks like you've done all the right things!