Composer_wrapper.php install failed!

What is needed to get the composer running?

Done:
su - librenms
./scripts/composer_wrapper.php install --no-dev

Result:
[librenms@~]$ ./scripts/composer_wrapper.php install --no-dev
Error: Failed to download installer signature from https://composer.github.io/installer.sig
Composer not available, please manually install composer.

What are the Steps to install the composer manually when you are behind an proxy?

wget https://getcomposer.org/composer-stable.phar > Done to /opt/librenms/ as user librenms << right?
mv composer-stable.phar /usr/bin/composer > Directory /usr/bin/composer doesn`t exsist.
chmod +x /usr/bin/composer

Server:
Centos 8 new installed.

Did you ever come up with a solution? I’m running into this issue and not sure how to proceed. I reran all the commands on the instructions on how to install LibreNMS on CentOS 8 with Apache (I am behind a proxy) and when it comes to running the ./scripts/composer_wrapper.php install --no-dev I get the error.

[root@usdet1lvdwb002 opt]# chown -R librenms:librenms /opt/librenms
[root@usdet1lvdwb002 opt]# chmod 771 /opt/librenms
[root@usdet1lvdwb002 opt]# setfacl -d -m g::rwx /opt/librenms/rrd /opt/librenms/logs /opt/librenms/bootstrap/cache/ /opt/librenms/storage/
[root@usdet1lvdwb002 opt]# setfacl -R -m g::rwx /opt/librenms/rrd /opt/librenms/logs /opt/librenms/bootstrap/cache/ /opt/librenms/storage/
[root@usdet1lvdwb002 opt]#
[root@usdet1lvdwb002 opt]# su - librenms
[librenms@usdet1lvdwb002 ~]$
[librenms@usdet1lvdwb002 ~]$ ./scripts/composer_wrapper.php install --no-dev
Error: Corrupted download, signature doesn't match for https://getcomposer.org/installer
Composer not available, please manually install composer.
[librenms@usdet1lvdwb002 ~]$