How about only one zpool in Ubuntu instead of bpool + rpool? Will zsys or anything like systemd mount generators be broken? Other concerns?

I am aware that grub does support only some of zpool features and usually this is the reason of having 2 pools.

Also 2 pools are used to encrypt only one (rpool) of them.

But that’s not a problem if I can make my mono-pool grub-compatible and apply options like encryption only to datasets other than /boot ?

In all zfs guides for linux I've seen they always create 2 pools and even the naming of them is unchangeable — I remember creating bpool which was named bootbool instead of bpool about 2 years ago and Ubuntu Focal failed to boot until I named it bpool. Because systemd mount generators or zsys was relying that the pools must be named exactly bpool and rpool.

Now with new Ubuntu Impish maybe I can keep it all in one pool?

I can make it grub-compatible (use only compatible pool features and /boot dataset options);

Have /boot in separate dataset but same pool;

Enable encryption only for non-/boot datasets.

Is it supposed to work or is it generally a bad idea (why then)?

I can check experimentally of course and see which problems will I face, but it'd be great to check the idea without too much hassle.

The benefits of mono-pool setup could be decreasing amount of entities (keeping the setup simpler), and increasing flexibility (sharing same storage capacity flexibly — if I need to restrict I can use quotas anyway).