NetBSD's native web server is called <bozotic httpd>. 
That small piece of software is dead easy to configure and is perfect to serve files over the web. 
All you need to do in order to set up your server, is adding something like:

httpd=YES
httpd_flags="-b -H -X -Z /usr/pkg/etc/letsencrypt/live/<mydomain.net>/fullchain.pem  /usr/pkg/etc/letsencrypt/live/<mydomain.net>/privkey.pem -z ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256"

To your /etc/rc.conf.

Understanding options:
- `-b`: daemon mode, detach from console
- `-H`: treat files starting with a period as hidden files
- `-X`: enables directory indexing; this is if you only want to serve
files and omit creating a index.html file on your server dir (by default /var/www)
- `-Z`: cert and private key paths
- `-z`:  list of acceptable SSL ciphers

Now put your files at /var/www and start the service.  The  default layout will look like that of https://cdn.netbsd.org
 Refer to <https://man.netbsd.org/httpd.8> for a more in-depth description.