RHEL 8 is supported from NMIS version 9.2.1G
On Debian 8, a compatible version of MongoDB Perl Driver (version 1.2.3 or newer) cannot be installed, even when CPANM is used.
On Ubuntu 16.04, pre-installing cpanminus, MongoDB Perl Driver and Mojo::File allows for a clean install of NMIS9:

• apt-get install build-essential cpanminus;
• cpanm --sudo MongoDB;
• cpanm --sudo Mojo::File;

If install of NMIS 9 fails due to failure to install package WWW::Mechanize, pre-install WWW::Mechanize before installing NMIS:

• sudo yum install -y perl-CPAN;
  sudo yum install -y perl-App-cpanminus;
  sudo cpanm WWW::Mechanize --sudo --notest;