I tried ZFS-on-linux with Ubuntu 21.10 and it ate my data (ZFS panics when accessing certain files). Sure, Ubuntu does have a habit of using unstable kernels, but I was still disappointed. It should be stable at this point.
I've never tried Ubuntu, but zfs has been rock solid on Fedora, Arch and Debian for me. Whatever the issue that hit you was, I hope recent versions of Ubuntu/zfs have fixed it.
curl is not installed by default in many distros
Also, I don't think it's possible to call external processes from within the browser sandbox
Which ones (apart from alpine)? I thought curl was pretty much as basic as it got and is always there.