I applied the bootstrap-v4 theme as described here
https://www.telerik.com/forums/support-for-bootstrap-4#0ycfPtGd9kqSuUyQ97z4mw
I noticed the menu control changes the text color to gray, so it kind of looked like the entire menu was disabled to me at first.
You can see it here
https://dojo.telerik.com/AKuPiXOL
It looks like kendo is setting this style. Not sure if this is intentional or not.
In my project I added this style to take out the kendo color.
:not(.k-context-menu).k-menu > .k-item{
color
: inherit;
}