@span mwl oh I'm the worst person to ask but here you go
personally: Debian LTS, with #ZFSBootMenu. I build my own #OpenZFS (dogfooding) but I'd have no issues running what Debian ships in the contrib repo. Setting up ZFSBootMenu is a little fiddly, but the docs are good and you only do it once
now all the "it depends", as all Linux-related answers must be. mostly, because I don't really think of OpenZFS as being a reason to choose Linux; if OpenZFS is the most important thing, then go for FreeBSD. so if you have to have Linux+OpenZFS, the choice depends on what you're doing
at minimum, something running an LTS kernel. anything that picks up a new kernel on day of release will have a bad time, because we usually don't have support for it in a stable OpenZFS release at that moment
if you don't need OpenZFS as the root/boot filesystem, then either a Redhat-ish or Debian-ish LTS. The RHEL-derivatives (Alma, Rocky) have probably the best support from upstream OpenZFS, since the big users are in education and research and those are almost exclusively RHEL. they don't ship it in their repos though; we provide package repositories for those. on the other side, Debian do ship it in their contrib repo, and their packagers work with us on the finer details, so its pretty solid
(in previous life as systems guy for a cloud service, it was Debian and locally-built OpenZFS, and it was just great)
if you do want OpenZFS as the root/boot, then I highly recommend ZFSBootMenu. it is basically an entire Linux+OpenZFS mini-distro in a UEFI binary as a bootloader, and brings things like FreeBSD-style boot environments to Linux. its is very very well thought out and understands the complications involved
I definitely _don't_ recommend GRUB for OpenZFS on root/boot, because it mostly doesn't keep up with new OpenZFS features, so you end up needing to keep a separate pool with a bunch of features disables, and you then need to take care to not `zpool upgrade` it (which, tbf, is a bit of a footgun in OpenZFS' tooling). it also doesn't really bring much to the table; iirc it doesn't understand snapshots/clones, and if you're not doing things like snapshot-before-upgrade, I'm not sure that OpenZFS root/boot is even worth the trouble
if you want OpenZFS in the installer, then options are far more limited. for general purpose Linux, I know Void Linux and CachyOS have installation options for OpenZFS. maybe Ubuntu too, though I'm never quite sure what the truth is on any given day. Void is by the same people that do ZBM, so that's very nicely integrated.
for "applicance" type things, Proxmox is popular, though I'd be more inclined to look towards TrueNAS CE because I know the OpenZFS devs there 😊 HexOS is an interesting-looking up-and-comer too. though really for an appliance-style usage, I'm far more likely to look towards a FreeBSD-based option (Sylve is looking _very_ interesting).
(disclosure on last para: I have in the past done paid dev work on OpenZFS for both TrueNAS and HexOS).
