> requires an active internet connection on the pi and my phone connected to the same network

MiniDNLA does not require the former if by "internet connection" you mean something with access to the WWW ("internet" can be taken more broadly to refer to any IP based network, which would include two computers with an ethernet cable etc). But the latter -- a network connection with the phone -- is sort of a logical necessity (if Foobar2000 has a feature to get around this, which is pretty unlikely, then that would require the phone and the Pi connected to the internet proper).

So for example: You should be able to do this by running a hotspot on the phone and connecting the Pi to that, while configuring the hotspot to prevent any connection beyond the phone.  You could also do it on a WLAN with no uplink (ie., a local wifi network not connected to the internet proper).