Ok, I just remembered I didn't share what I was using on Android.

6) play.google.com/store/apps/det (and other apps from this dev)

@TheFuzzStone
DAVx^5, formerly known as DAVDroid, it syncs your contacts, calendar and tasks with Nextcloud instance, great alternative to Google contacts, calendar etc.
davx5.com/

A Mastodon instance for maths people. The kind of people who make $\pi z^2 \times a$ jokes.

Use $ and $ for inline LaTeX, and $ and $ for display mode.