very nice job ! @falk
Answer probably too late, but I still agree.
GMP scanners are controlled by the GMP managers present on each slave, so it is necessary to specify to the GMP of the slave the number of hosts it is able to scan.
It is therefore necessary to run gvm with this option like this for centos /etc/sysconfig/gvm
for /16 scan possibility :
Or directly in the systemd service