And if you look at the history page of Flatpak, you'll see that the project has been in development in some form or another for roughly 20 years https://github.com/flatpak/flatpak/wiki/Flatpak's-History

My spidey sense is tingling towards Rust as to the language of this rewrite.

I had a nightmare last week wherein I read a headline that systemd was writing its own kernel. When I woke up I realized it was a possibility, after all it has replaced GRUB. https://wiki.archlinux.org/title/Systemd-boot

I wouldn't recommend reading that comment thread, it immediately jumps into "this is fascism!" which is why it's hard to take people seriously sometimes.