But, you can still use Let's Encrypt with old Android devices until the later part of 2021 using the alternate chain: https://letsencrypt.org/2020/11/06/own-two-feet.html (As a point of reference, Caddy supports configuring this alternate chain.)

Sectigo is the new name for Comodo. The same bunch of pricks who tried to trademark “Let’s Encrypt”.

Other players in the acme cert “business” is great. Renaming a slime ball name and carrying on like nothing happened is not ok.

Yes. The intermediate certificate has been included since Android 6.0 [1] and the root expires in 2038 [2].

[1] https://android.googlesource.com/platform/system/ca-certific...

[2] 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 :-/

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