Running Pi-Hole on an Orange Pi Zero (256MB RAM) without crashing

Default setting for Pi-Hole causes it to run out of ram on a 256MB system such as the ultra-cheap Orange Pi Zero,

Suggested changes:
edit fastcgi-php to run less cgi processes e.g.
nano /etc/lighttpd/conf-enabled/15-fastcgi-php.conf
and change
 "PHP_FCGI_CHILDREN" => "2",

(from 4 child processes)

also change 

nano /etc/php/7.3/cgi/php.ini

and set

memory_limit = 64M

(instead of 128M)

That should do it