While Google’s Home Mini is a solid smart home speaker, the device is missing one significant feature when compared to its main competitor, Amazon’s Echo Dot: the low-cost speaker doesn’t feature a line-out auxiliary jack, or even a standard way to connect to an external speaker.
If you want a higher-end sound, the only option you have is to stream to a Chromecast-equipped speaker system, which aren’t very common.
Intrepid modders at the YouTube channel SnekTek have added a standard 3.5mm aux audio port to the mini through a rather complicated homebrew process. The procedure is pretty complicated and involves boiling adhesive off the bottom of the device, locating a space where the headphone port actually fits, and even going so far as to carve a hole in the smart home speaker.
The hack doesn’t disable the Mini’s built-in sound, but seems to work quite well if the above video is accurate. While interesting, it’s probably easier to just purchase an Amazon Echo if connecting to a speaker via an aux cable is something you want to do.