fred@fourth:~$ sudo groupadd mygroup
[sudo] password for fred: 
fred@fourth:~$ sudo usermod -a -G mygroup fred
fred@fourth:~$ sudo usermod -a -G mygroup root
fred@fourth:~$ getent group mygroup
mygroup:x:1001:fred,root
fred@fourth:~$ 
fred@fourth:/opt$ sudo chown root:mygroup scripts
fred@fourth:/opt$ ll
total 16
drwxr-xr-x  4 root             root    4096 Dec 30 04:10 ./
drwxr-xr-x 19 root             root    4096 Dec  2 20:03 ../
drwxr-xr-x  4 systemd-coredump root    4096 Sep 26  2020 digitalocean/
drwxr-xr-x  5 root             mygroup 4096 Dec 30 04:13 scripts/
fred@fourth:/opt$ sudo chmod 770 scripts
fred@fourth:/opt$ ll
total 16
drwxr-xr-x  4 root             root    4096 Dec 30 04:10 ./
drwxr-xr-x 19 root             root    4096 Dec  2 20:03 ../
drwxr-xr-x  4 systemd-coredump root    4096 Sep 26  2020 digitalocean/
drwxrwx---  5 root             mygroup 4096 Dec 30 04:13 scripts/
fred@fourth:/opt$