I know it's less convenient, but there's dedicated WiFi hotspot devices that exist.

I considered getting a "dumb phone" and one of these devices because in some cases a tablet-style internet-only plan + pay-as-you-go minutes for the odd time I use a phone would be cheaper than a bundled smartphone plan.

At this point saving the $10/month isn't worth the hassle to me though and now I use Slack on my phone so damn much it'd never work :\

Look at the new Nokia 'matrix phone' 8110. It is a dumb phone with some smart features and most notably 4G and WiFi hotspot functionality. At only 80 dollars or so. I am seriously considering getting one just as an experiment

Thank you very much.

Sounds exactly like what I'm looking for.

Symbian phones, sadly now dead (yes I don't miss Symbian C++, but the phone was great).

IIRC Nokia had one.