If you have an existing default installation (btrfs for Fedora desktops), you can reuse the existing "home" subvolume. There are a couple of tricks to make it possible. This is a bit verbose and technical, but is designed for Fedora QA to test that this continues to work as expected. https://fedoraproject.org/wiki/QA:Testcase_partitioning_custom_btrfs_preserv...
Another idea for auto-discovery is a "discoverable subvolumes specification" similar to the already existing Discoverable Partitions Specification. It's not limited to btrfs subvolumes, supporting plain directories following the naming scheme. Plausibly also LVM. We'll just have to see if this gains traction at some point. Of course it would also need installer integration. https://lists.freedesktop.org/archives/systemd-devel/2021-November/047059.ht...