Dear Dario,
indeed, the gpg key from @mhall119 is no more valid but there’s the solution on: https://repos.influxdata.com
In case,
if you have already done what @mhall119 suggested, you first need to delete the files you have created:
sudo rm /etc/apt/sources.list.d/influxdb.list
sudo rm /etc/apt/trusted.gpg.d/influxdb.gpg
Then, follow the Debian procedure from https://repos.influxdata.com:
wget -q https://repos.influxdata.com/influxdata-archive_compat.key
echo '393e8779c89ac8d958f81f942f9ad7fb82a25e133faddaf92e15b16e6ac9ce4c influxdata-archive_compat.key' | sha256sum -c && cat influxdata-archive_compat.key | gpg --dearmor | sudo tee /etc/apt/trusted.gpg.d/influxdata-archive_compat.gpg > /dev/null
echo 'deb [signed-by=/etc/apt/trusted.gpg.d/influxdata-archive_compat.gpg] https://repos.influxdata.com/debian stable main' | sudo tee /etc/apt/sources.list.d/influxdata.list
Cheers,
