Yeah grep recursively "-R" through all files matching pattern "/etc/dnsmasq.*".
Grep for lines starting with a hash "^#" or "\|" empty lines "^$" and invert "-v" the results.
And sort the lot.
If you would have changed below directive in dnsmasq.conf:
conf-dir=/dnsmasq.d/,*.conf
I would have had to change the grep into:
sudo grep -v '^#\|^$' -R /etc/dnsmasq.* --include=*.conf | sort
Furter on this, as you only need extra IP's to listen/bind to, you could have done without the dummy interfaces and use IP aliasing on one interface instead: