How to rotate group name in grouped bar chart?

I am using a grouped bar chart.
A simplified example is shown here:

The number of entries varies, and often can be large.
This causes the group headings (e.g. “Model1”, “Model2”) to overlap as they are all being displayed horizontally.
The tick labels seem to auto-rotate when there are many entries, but this does not rotate the group titles.

I have tried using ‘tickangle’ and ‘textangle’, but they don’t affect the group titles.
What to do in this case?

I was wondering if there is some work around to this?
Possible to have ellipsis to shorten the text? The problem with trying to do this manually (cropping the length) is that the cropping can result in different labels being converted to identical representations (e.g. [LongText_Model_A, LongText_Model_B] -> [LongText_Mo, LongText_Mo] based on the cropping length. As it has to serve a large variety of inputs, it is difficult to hard code such a value.