With alternative packaging solutions no longer options for getting GNUnet. I thought of something else which someone also suggested on SE: What if there is a sid minimalist chroot to safely install the latest version? Debootstrap or something better for the task (see more in the lInk) could be used for this. Some directories like home could be mounted so gnunet and related whonix tools could interact.
Pros: No longer have to wait for major steps by upstream projects for packaging. No extra package management solutions need to be added updated.
Cons: Chroot may need many packages. Needs to be tested if the concept is sound.