Using flatpack-0.9.10 with tinycorelinux:

$ flatpak remote-add --user --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
$ flatpak install --user flathub org.libretro.RetroArch
Required runtime for org.libretro.RetroArch/x86_64/stable (org.freedesktop.Platform/x86_64/1.6) is not installed, searching...
Found in remote flathub, do you want to install it? [y/n]: y
Installing: org.freedesktop.Platform/x86_64/1.6 from flathub
...
[####################] 4 delta parts, 33 loose fetched; 114054 KiB transferred in 163 seconds
pivot_root: Invalid argument

$ flatpak run org.libretro.RetroArch
pivot_root: Invalid argument

Is this because the tinycore initrd is loaded into ramdisk which is an actual file system and initramfs is not a file system. For initrd pivot_root is used and for initramfs switch_root is used. You cannot use pivot_root on an initramfs rootfs, you can only pivot real file systems?

Is there a way around this?