I've got a Galaxy S4, which is stuck at at 5.0.1 (not even the latest Lollipop). After many hours of experimentation, Google searches, trial and (mostly) error I've gotten CM13 running on my main phone. The biggest problem was getting data to work on Ting (Sprint MVNO), but this morning I found a magical patch that somebody had made and posted.
So if I make a reasonable effort I can keep my S4 patched, yay! But I also realize it's not for everybody; two of the other three S4 phones in my household are still on stock ROM because the users aren't as fiddly as I am. (But they are also out of room, if only because their phones have a butt-ton of useless apps they can't uninstall. Thanks, Google. Thanks, Samsung. Thanks, Sprint. Anybody else want to put their crap on my phone? Because there's still room, as long as I don't actually turn it on and try to use it.)
The fourth S4 is a spare Freedompop phone I use to experiment on. There's a certain symmetry in the fact that the Ting patch is just a modified version of the patch I use on the Freedompop phone.
So hey, that's me sorted. But it's a hassle I shouldn't have had to engage in any more than Trevor. But at least I'm not an entitled millennial dick. Me, I'm an entitled baby boomer dick.