Reporting back in.. Still syncing my Calcurse config/data from my local Nextcloud server to Termux (bash alias) on the surprisingly useful 2017 Kindle Fire 7". Tying in notifications generated from shell scripts or Python programs to the Android notification system is possible. Can't say I use termux-notification as often as simple bash/python scripts or the Ranger file manager, but it's a nice feature to play around with. Actually, quite a few of the gifs I've converted from mp4 to gif to post on the forum were pulled with youtube-dl using Termux.
tl;dr - termux-notification, calcurse, ranger file manager, youtube-dl (gif memes), bash/python scripts, my vim config/plugins ported fine
I'm not recommending ASCII or TUI tools for casual users--if you're already using such things Termux can be a fine extra toolbox.