The most impacting technical event of the Internet was the expiration of the Letsencrypt DST Root certificate which brought a lot of grief to technical support people and owners of declared obsolete devices. Here is the lists of compatible and incompatible devices provided by Letsencrypt.
There is a way to make some of incompatible devices work, by manually installing ISRG Root X1 Letsencrypt certificate, here is brief instruction for older Apple OS, and below I will show how to do the same on Android 6.0.1 phone.
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