There's been so many of these lately.
I really need to share a blog post on doing this exact thing with a VPS, 2 commands to install and setup lxd.
And then client side bash function to just make and connect via tmux and delete when you're done.
Self hosting these services is too easy to do and you can have more control of your data and better specs.
On this same idea, I just started working on shelley-lxc: https://github.com/jgbrwn/shelley-lxc
Work in progress/alpha, but the core functionality works as a proof of concept. Super exciting working on this kind of stuff.
It's funny to me as well. Being initially inspired by Yelp's dockersh I wrote a functional MVP of the same concept around 2 years ago. It used a custom Go sshd-proxy to spawn kata-container backed pods in kubernetes. I used it personally for a very brief period of time, and found it useful as a small timesaver for testing things. I wasn't comfortable with monetizing it though. After seeing a few of these pop up, I realize maybe I missed my chance to be early.
As far as self-hosting goes, it looks like there are some FOSS projects now, eg https://containerssh.io/