Certificate failure in a mobile application, how to overcome?

Question

Android

The bottom line is that the application worked successfully for some time and suddenly errors began to appear.
The application is connected to the backend and made requests via https, at some point everything went wrong, and not for all clients.
I looked in the news, it turns out that this is described https://www.opennet.ru/opennews/art.shtml?num=55875

Suggesting to install new certificates on devices, as you yourself understand, is an idea.
Therefore, the api was urgently transferred to http, since there is only insensitive data there.
But I don't think it's very good.

As always, there are the dumbest options to buy a paid certificate, but you need a wilcard, it strains
the second score and use http
the third is to forget about the old people and use only new devices, this is not very good because a lot of users are on old ones
In general, share your thoughts on this problem