After today’s upgrade of ‘apt’ package up to version 2.9.16 on Sparky testing “Seven Sisters” based on Debian testing “Trixie” ONLY (not stable, not oldstable), you can find such APT issue:
https://repo.sparkylinux.org/dists/core/InRelease: The key(s) in the keyring /usr/share/keyrings/sparky.gpg.key are ignored as the file has an unsupported filetype.
To fix it, do:
Copy Sparky GPG key:
sudo cp /usr/share/keyrings/sparky.gpg.key /etc/apt/trusted.gpg.d/sparky-repo.asc
Change the GPG key in the source list:
sudo nano /etc/apt/sources.list.d/sparky.list
from:
signed-by=/usr/share/keyrings/sparky.gpg.key
to:
signed-by=/etc/apt/trusted.gpg.d/sparky-repo.asc
Then refresh package list and upgrade packages:
sparky-upgrade
or:
spu
or:
sudo apt update && sudo apt upgrade