I have tons of old phones, I'd like to use them as IOT devices. Anyone know a really small Android rom with no extras? Not only no Playstore, but also no fancy theme engine etc, so I can use them as servers etc

I started an e2e encrypted Dropbox clone, meaning file names and contents get encrypted client side prior to uploading. It also has a fairly advanced system for sharing links to files etc. But I got stuck at PDF previews which can't be generated on the server cause the file can't be decrypted there and I never finished it.

To all who use CSS:
Do you vertically align using flexbox or some weird old hacky method? I just used flexbox throughout a personal project to find out it doesn't work on my mom's computer...
Sorry if this question is too serious for this, but it really bothers me :D