Adding to the many other great uses of termux already here, the most useful lately for me is running Syncthing. After the "drama" with the Syncthing android client (my understanding: official development stopped due to onerous requirements from the Google, then the most popular fork was transferred to a new owner in a less-than-fully-trustworthy manner), being able to just run syncthing from the command line is a breath of fresh air.
I highly recommend using Unexpected Keyboard along with termux (a recommendation I myself almost certainly got from HN).
I remember hearing something about the circumstances of that transfer, do you have a link/reference. Also, when you run Syncthing (the normal build I assume, without the Android wrapper), are you able to reliably prevent Android from killing it?
Last things first: on my phone I only run syncthing "on demand", so I can't actually answer your question. Maybe someone else can chime in? From the little I've brushed up against the issue you're referring to, I think there's a way to have it not get killed, but it seems like it might be a little bit of a hassle.
No shortage of reading if you have the time! I'm quite happy to be running just the "standard" package (although, yeah, I should've pointed out that I don't run in continuously on my phone...)
Not commenting on the larger gist of the comment, only:
> I've been having RSI pain on my right hand due to using mouse too much and in un-ergonomic positions
If you can, try using a left-hand vertical mouse. I use an Evoluent but there are a million brands. Get a cheapo and try it out. I figure it took me about a week to adjust and my wrists have been happier ever since.
Similar to a sibling comment, and perhaps not really applicable (since this isn't a company making something people can buy...), but the MNT Reform is amenable to fitting a custom/ergonomic keyboard also (I hadn't seen the Framework in the sibling comment, it looks very cool!).
I don't know how to link to it directly, but midway down this article there's a picture and some more links of an MNT Reform (apparently completely home-built) with a very cool, "thumb-centric", column staggered ergo keyboard:
