Add an aria-label with the chart type. Add aria-current="true" to the button that is currently selected as well.
_Bonus points_: These really shouldn't be buttons are at all - it's a radio group. Ideally, radio inputs would control this under the hood and would visually be replaces by whatever you want (this is how single selection button groups work in EUI too).
The selected state for the current suggestion looks a lot like (is?) the EUI focus state for a lot of controls. This is pretty confusing when other things on the page are focused and will probably become more confusing when focus states are returned to the other suggestions.
Relevant WCAG Criteria:
Pinging @elastic/kibana-accessibility (Project:Accessibility)
Pinging @elastic/kibana-app (Team:KibanaApp)
@MichaelMarcialis Can you suggest another style for the currently active suggestion which is not looking like the regular EUI focus state so we can use that one for focus?
This is how it looks like right now:

The currently active suggestion is using the blue outline normally used for the focused element, but the actually focused element (the donut chart) is only shown by a very slight y translation.
Hi @flash1293 @MichaelMarcialis @myasonik, I submitted a draft PR with one of the solutions – we could either:

Let me know your thoughts!
I like the default focus state if we get rid of the underline text decoration (so just darker background)
@flash1293, @mbondyra: I've worked up a quick concept for the suggestions focus states. Have a look at the links below and let me know if you're good with this direction. Happy to hop on a Zoom as well, if desired.
Suggested changes include:

As a side note, I noticed that selecting one of the suggestion options doesn't currently move the "Current" text to that new selection. Is this intentional or is it a bug?
I don't have a strong preference, both seem equally fine to me. Based on the interaction to get into these states I don't think either is confusing to the user.
As a side note, I noticed that selecting one of the suggestion options doesn't currently move the "Current" text to that new selection. Is this intentional or is it a bug?
This is intentional, if a suggestion is selected you are in a "preview" state and can still go back to your "real" current visualization. The actual suggestions are always based on the "Current" visualization to the left. As soon as you start editing or press the refresh button to the right of the suggestion, it "commits" the suggestion and it becomes the new "current", providing you with a new set of suggestions based on the current visualization.
This confused some people before, I'm happy if we can come up with a better flow here, but I would like to keep it off this PR and treat it with a low priority.
@myasonik the amount of !importants (6 and I still didn't style it properly) I have to add to make this work as EuiButton doesn't make it worth. In fact we override almost all the styles. I'll leave it as EuiPanel that sematically is also a button.