corpo-disko-images> setting up /etc...
corpo-disko-images> Initializing machine ID from random generator.
corpo-disko-images> File system "/boot" is not a FAT EFI System Partition (ESP) file system.
corpo-disko-images> Traceback (most recent call last):
corpo-disko-images>   File "/nix/store/hk9khalas7ig9lpd8xygb00jgx9kjv2d-4d4f3f52hgwgk63d4fjg1rj4c1jdg9mn-systemd-boot", line 394, in <module>
corpo-disko-images>     main()
corpo-disko-images>   File "/nix/store/hk9khalas7ig9lpd8xygb00jgx9kjv2d-4d4f3f52hgwgk63d4fjg1rj4c1jdg9mn-systemd-boot", line 377, in main
corpo-disko-images>     install_bootloader(args)
corpo-disko-images>   File "/nix/store/hk9khalas7ig9lpd8xygb00jgx9kjv2d-4d4f3f52hgwgk63d4fjg1rj4c1jdg9mn-systemd-boot", line 292, in install_bootloader
corpo-disko-images>     subprocess.check_call([f"{SYSTEMD}/bin/bootctl", f"--esp-path={EFI_SYS_MOUNT_POINT}"] + bootctl_flags + ["install"])
corpo-disko-images>   File "/nix/store/vbfsfi87f7ks3hndbvn72n4334f9xll0-python3-3.11.9/lib/python3.11/subprocess.py", line 413, in check_call
corpo-disko-images>     raise CalledProcessError(retcode, cmd)
corpo-disko-images> subprocess.CalledProcessError: Command '['/nix/store/wh5wyrs4nxdx7kh3ip0psn11rc2kknl1-systemd-255.4/bin/bootctl', '--esp-path=/boot', '--no-variables', 'install']' returned non-zero exit status 1.

corpo-disko-images> + /nix/store/gc39rhvazg28s7y80c4c0a24x3hsv92p-postMountHook.sh
corpo-disko-images> + rm -rf /tmp/tmp.qOc2Qrmj2x
corpo-disko-images> warning: the group 'nixbld' specified in 'build-users-group' does not exist
corpo-disko-images> cp: cannot access '/nix/store/flqdgxi79hgv69k8vc1rdcxvn30m0i3r-perl5.38.2-HTTP-Cookies-6.10': Cannot allocate memory
corpo-disko-images> cp: cannot access '/nix/store/fzh5aadrdl76f7cn930ls979x6cgblyd-libsoup-2.74.3/share/locale/gl/LC_MESSAGES': Cannot allocate memory

I'm interested into trying bcachefs with encryption using disko and I saw that there is a PR which is blocked because it should an abstraction for supporting multiple devices should be implemented before.
I also saw there is another PR for supporting subvolumes.
Would a PR where I try to integrate both the attempts together be appreciated? In terms of interface would you like something similar to the first proposal in this comment?

 disko.devices = {
    disk = {
      x = {
        type = "disk";
        device = "/dev/nvme0";
        content = {
          type = "gpt";
          content = {
            type = "bcachefs";
            label = "ssd.ssd1";
            pool = "rpool";
          };
        };
      };
      y = {
        type = "disk";
        device = "/dev/sda";
        content = {
          type = "bcachefs";
          label = "hdd.hdd1";
          pool = "rpool";
        };
      };
    };

    bcachefs_pool = {
      rpool = {
        type = "bcachefs_pool";
        mountpoint = "/";
        passwordFile = "secret.key";
        subvolumes = {
            "/home" = { };
            "/nix" = { };
            "/testpath" = { };
            "/testpath/subdir" = { };
          };
      };
    };
  };

In reply to @lassulus:lassul.us
I answered in nixos-anywhere, but I can also answer here