Kernel 5.4.51-v7l+ is the latest kernel for the 32-bit Raspberry Pi OS on the Raspberry Pi 4. But you may want to think before you update, especially if you use the Pi for media consumption.
There is a glitch with kernel 5.4.51-v7l+ when used with Chromium Media Edition, a version of Chromium with support for streaming services such as Netflix, Hulu, Prime Video. The glitch will cause full screen video to corrupt, but normal windowed video will playback with no issue. It is sad to see this issue given that Chromium Media Edition has such great playback with older kernels.
The issue was identified by leepspvideo as part of his latest video comparing Netflix and YouTube playback with stock and Media Edition Chromium. In our own tests we hit the same graphical corruption in full screen mode. We contacted Gordon Hollingworth, Director of Software Engineering at Raspberry Pi Trading and he confirmed that there was “bug in the firmware which we released with the 5.4 kernel, this has now been fixed and doing apt update will get the latest version in which this isn't a problem.” Gordon later confirmed that the full screen video issue is caused by the Chromium Media Edition script disabling the composite manager, xcompmgr to reduce screen tearing. Restarting xcompmgr will fix the issue but it will see the return of screen tearing.