I observe some problems with the image, in 1.14.2 everything was fine. Watch the video
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You're filming your monitor. Is the issue visible if you use a screen recorder to record your screen? If not, this is probably an issue with your monitor.

Well, yes, the problem with the monitor 😛. In 1.14.2 everything is fine, in 1.14.3 there is a problem with the monitor. The video shows everything
Please attach a video made with a screen recorder. If the file size is too large, please upload it somewhere else and link to it here.

I technically can't do this. Because of problem MC-153714 , when I try to start recording a screen, I have fps in a game down to 10 and this does not allow to capture video the problem.
Hmm. This is very odd indeed. I found another ticket that is about the same issue as well: MC-154271. I'll resolve this ticket as a duplicate, as we don't need multiple tickets about the same issue. Feel free to add any details to that ticket, if you have any.
Edit: The only thing that comes to my mind right now that could potentially have caused this issue is the update to a newer version of LWJGL, which was done in order to fix some issues on Linux.