We have relied on Universal SSL for a number of years. On May 17, 2023, Cloudflare issued us a new certificate issued by Google Trust Services LLC, and we lost our connections to older devices such as those running Android 8. This affected many other Cloudflare customers, no doubt, as discussed in this topic:
The issue seems to be that the certificate chain is not complete for these devices. This affected our mobile app users and some digital signage installations.
The fix seems to pay for Advanced Certificates and specify Digicert, which is fine, but the documentation should be updated. And I would like to know how to get warning of this type of discontinued feature in future.
My understanding is this issue is now resolved, and any future certs will work on old Android versions. You should be able to disable Universal SSL, wait a few minutes, enable, and then get issued a new cert. If disabling Universal SSL and losing HTTPS for a few minutes is not an option for you, please create a support ticket and post the ticket number here. One of the nice MVPs here should be able to get it escalated for you. Cloudflare Support can then manually reissue the certificate, but it may take a few days.