Installing cert on Android

I am a noob to androids and they all seem to be different.

Basically, I download the CER convert to a DER then upload to a WeTransfer link since Outlook likes to block those.

Apple, although clunky, seems to be consistent in the installation. However, from the Download to the Certification trust area on Android, I can’t find a reliable end user tutorial (especially with pictures).

Does one exist?

How do other role this out?

MDM would be the logical choice. Still looking for a good low cost solution. Apptec360 seems like it fits the bill but I haven’t completed testing yet.

But for shops with 20 or less users using their own phones may make that prohibitive.

I get that and that page is what I built my iOS install guide off of, but that is after you convert to DER then transfer it to a hosting site since outlook usually blocks then you have end users that know nothing about this and android tends to be non standard.