No valid OpenPGP data

hello, my system:
Distributor ID: Ubuntu
Description: Ubuntu 20.10
Release: 20.10
Codename: groovy

Linux homeserver 5.8.0-63-generic #71-Ubuntu SMP Tue Jul 13 15:59:12 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

my first command is,
wget -q “https://maven.xwiki.org/public.gpg” -O- | apt-key add -

the output is:
Warning:
apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
gpg: no valid OpenPGP data found.

unfortunately I have no idea what to do there
can someone help me?

many thanks

First time I see this, I guess it’s new. I wonder what is the new standard now.

Anyway it does not explain why it does not work for you, since apt-key is supposed to keep working, it’s just not recommended anymore.

Could you try just wget https://maven.xwiki.org/public.gpg to make sure you can actually download that file? Maybe the download fail for some reason in your case (like a proxy that prevent it) and it try to add as GPG an error message.