My phone died (well, stopped connecting to cell networks), so I am busy procuring another...
No need for advice. I have done every troubleshooting suggestion, from the obvious to the obscure reddit suggestion. Pretty sure it's a hardware failure (50 cent part, 80 dollar repair job kinda thing) It's a 3-year-old cheap android (and was an older model when I bought it) and am due for an upgrade anyway.