Jolla had similar concept too at 2013. I had one and back then it was really, really nice phone. Maybe not in a sense that flagship models from big vendors were, but I really enjoyed the UI and modular options was a huge selling point at least for myself. Then they started to work with a tablet which failed on pretty much all fronts and the whole company practically disappeared.
ZFS in general is pretty memory hungry. I set up my proxmox sever with zfs pools a while ago and now I kind of regret it. ZFS in itself is very nice and has a ton of useful features, but I just don’t have the hardware nor the usage pattern to benefit from it that much on my server. I’d rather have that thing running on LVM and/or software raid to have more usable memory for my VM’s. And that’s one of the projects I’ve been planning for the server, replace zfs pools with something which suits my usage patterns better, but that’s a whole another story and requires some spare money and some spare time, which I don’t really either at hand right now.