For people with a mouse the Play page interface looks like this:
(I had to freehand draw the mouse pointer, since my screen capture doesn’t take it)
So people with a mouse can know why ineligible challenges are so labelled.
But people with a smartphone can’t hover their finger… so, is there any solution to that?
[pedant mode on] Yep, actually they can hover their finger over the phone, but they don’t get the same result [pedant mode off]
[language learner mode on] Are my phrases correct? “why they’re so” and “why ineligible challenges are so” sound weird to me but I can’t find an alternative [language learner mode off]
So people with a mouse can know why challenges are ineligible.
As an aside, all of your sentences were perfectly legible. But as you noted they sounded a little unnatural. I think my two propositions would sound more natural.
Are there still bugs in the eligibility logic? I used to find a game would be marked as ineligible when I was not outside the rank range. My guess was it was comparing the wrong of the many different ranks an account has.
Also I think if someone has blocked you then it lies and doesn’t tell you that’s why you’re ineligible. I don’t know if that’s a bug, or on purpose to stop you being angry.