I got fed up with this and ran across ulefone. Some of their phones are downright ridiculous but I'm happy with mine.
It's a waterproof brick with good grip and a 10,000mAh battery. Good for up to 4 days. It's also got rubberised grips and takes a beating. Oh, it also has a headphone port, and thermal imaging.

I've not tried reflashing, but the os seems mostly vanilla android. I've had a couple of OS updates since I got my phone, so it's not just fire and forget. I'm not sure about long term however. You might also have issues with the thermal camera, if you reflash. I don't know how it's wired internally, and whether a non custom app will play nice.
They seem to be aiming at builders/workmen as a rugged phone with long battery life. They also seem to be trying to build a proper brand, not just a throw away one. Hopefully that means they will at least do security updates for quite a while. But that's speculation.
Oh, and it's a brick, weight wise. I personally like that, but it's quite polarising when people try it.