Just discovered PlainApp last night and I thought it could be useful to others who want to manage their phone from their desktop.
I’ve installed it on my Kompakt and it works great so far! I wasn’t able to access it on Firefox, but that could be due to all of the blockers and extensions I have installed there. Chrome is fine.
The phone app itself contains a Markdown notes app, Pomodoro timer, and other small utilities. Turn on the server to access through your desktop browser when connected to the same network. There you can manage files and contacts, view your SMS and call logs, and even get desktop notifications. And you can sideload APKs!