Interesting, as I was just about to post here that since updating to the latest Open XR Tools (and Toolkit) I also have lateral (not quite horizontal) jitter. Not sure if this is what you are getting but I only really noticed it at night with stars, where each star turns into three! I then noticed jitter in the pull-down menus. Interestingly the ground scenery, buildings, etc and the cockpit don’t seem to be affected.
After a bit of testing I found that it only happens with motion reprojection and when the new option on NVIDIA flow acceleration function is allowed. When this option is disabled (still using MR) then the jitter stopped.
Never seen this problem before (i9, RTX-3090 ,G2 and latest version of Win 11).
Update, as per request: DX12, HAGS off.