How to delay a service startup (i.e. don't run at boot time, but start later)?

[Chris Green]

I have a service (minidlna to be specific) that I want to leave 'as
installed' from the Ubuntu repositories but I don't want it to start
at boot time.  I need to start it later after a number of file systems
have appeared.

So is there a way of disabling start at boot time but allowing
'service minidlna start' some time later?

It's an init.d script (i.e. there a file /etc/init.d/minidlna) but I'm
running a standard Ubuntu 20.04 setup where systemd actually manages
the init.d scripts.

-- 
Chris Green