For now: Give Jujutsu (https://jj-vcs.github.io/jj/latest/) a try, it's good whilst maintaining a level of compatibility with git which is good for gradual adoption and uptake.
Avoid: Pijul. I doubt it will succeed in getting wide adoption. Some of the reasons already covered by others comments in this thread so don't want to repeat.
Wish: I really wish darcs was rebooted and made a comeback. What can we do to make it happen? I heard a version 3 is a work in progress. I am also aware of this new initiative (GitHub equivalent but for darcs): https://smeder.ee
Based on the fact that your ideal is to have a similar experience to heroku than managing your own server setting up reverse proxies take a look at these options:
1) https://dokku.com - lets you turn your light sail instance basically into heroku
These look like great options, I'll check them out. Dokku looks like it could be a good balance between offering a managed server experience while letting me deploy multiple apps to a single instance