> … ZFS was a huge selling point, but I heard that it works quite well on Linux, these days. …

True.

I have OpenZFS-native encrypted root-on-ZFS for Kubuntu 25.10, made ultra-simple by the installer for Ubuntu (25.04 at the time).

FreeBSD can not yet do this. Please see, for example, https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=263171

> 263171 – add loader(8) and boot loader menu support for boot with OpenZFS-encrypted ROOT