apt-get update "The following signatures were invalid..."

[jsch]

tee is splitter. The data read from stdin (in our case curl) is sent to a file and to stdout. Since tee is started as root (hence sudo tee), the file is written as root.
A cleaner way is:

Code:

curl -s https://repo.mobian.org/mobian.gpg | sudo tee /etc/apt/trusted.gpg.d/mobian.gpg > /dev/null

By sending the stdout to /dev/null, it is simply not displayed.
Can you please check if the timestamp of the file /etc/apt/trusted.gpg.d/mobian.gpg matches the time when you ran the command from above (w/ or w/o >/dev/null).