It seems that there is no real alternative... Let's Encrypt's move is going to obsolete a huge lot of devices :-/
That doesn't matter, the root that signed the intermediate cert was created in 2010 [1] which means it's usable for Android>=2.2.
[1] https://crt.sh/?id=1199354
It seems that there is no real alternative... Let's Encrypt's move is going to obsolete a huge lot of devices :-/