This is what the System check widget on the Admin overview shows a warning about UTF8mb4 when I hover (ignore the other warnings, they are all valid):
This is what I see in the (full) System Check:
I guess the problem is, that the overview simply tries to place the results (you can see in the details) into the tooltip, which doesn't work properly in some cases. Maybe we should simply remove the tooltips to avoid irritations.
Kind of related to #17627
Maybe could also think about removing line breaks etc then it might work again (and/or strip html)? It could be quite useful to have these tooltips but if not easily doable we can remove the tooltips 👍
To reproduce the problem, run this in mysql as root:
SET GLOBAL local_infile = 'ON';