Live iso doesn't seem to have support for btrfs-progs. Which is necessary for installing a system in subvol.
Which ISO are you referring to? Please give a link.
Minimal Installation CD: https://www.gentoo.org/downloads/
Please give the precise ISO filename you used. As far as I can tell, it should be in there: ``` $ rg btrfs-progs releases/specs/x86/hardened/admincd-stage1-openrc.spec:172: sys-fs/btrfs-progs releases/specs/sparc/sparc64/installcd-stage1.spec:73:# sys-fs/btrfs-progs releases/specs/x86/i486/installcd-stage1-openrc.spec:81: sys-fs/btrfs-progs releases/specs/ppc/ppc32/installcd-stage1.spec:66: sys-fs/btrfs-progs releases/specs/amd64/installcd-stage1.spec:82: sys-fs/btrfs-progs releases/specs/amd64/livegui/livegui-stage1.spec:228: sys-fs/btrfs-progs releases/specs/amd64/hardened/admincd-stage1.spec:173: sys-fs/btrfs-progs releases/specs/arm64/installcd-stage1.spec:84: sys-fs/btrfs-progs releases/specs/ppc/ppc64le/installcd-stage1.spec:82: sys-fs/btrfs-progs releases/specs-qemu/alpha/installcd-stage1.spec:50: sys-fs/btrfs-progs ```
I can confirm it's available in latest version. Sorry I made a mistake on my side.