A YouTuber has given his Google Home Mini an auxiliary port because he says that his speaker is "too quiet." Google's Home Mini is definitely not meant to be the loudest speaker out of the crop of products that Google offers in this lineup, but it seems that some users weren't sure what to expect in regards to the audio output volume. YouTube user SnekTek's solution was to give the speaker the 3.5mm audio port so that an external speaker could be plugged into it and have the connected speaker be the source for the outgoing audio.
The results actually appear to end up better than one might hope, and this probably isn't too much of a surprise if you actually know what you're doing. While the process may not be that complex it does seem to be a time-consuming affair and is probably not something that users should try unless they're absolutely sure that they will be able to complete the installation properly. The good news is that the YouTube video gives a pretty good explanation of how to install the port, and it's a fairly detailed video at that so it should be pretty easy to follow along with.
That said it should go without saying that this is probably going to void the warranty on the speaker if you attempt to insert an audio port into your own Google Home Mini. Or if you haven't purchased a Google Home Mini yet and were considering buying one, it might be worth considering buying the Google Home or Google Home Max instead if good audio quality with a higher volume output is a bigger concern for you in choosing one of Google's smart speakers. Another thing to consider is that if you do choose to attach an audio port to your Google Home Mini speaker, audio is going to come out of both the speaker inside of the Google Home Mini and the speaker that's plugged into it, so if you don't mind having doubled up sound then this is a sort of roundabout solution that can give you what you're looking for, if what you're looking for is to have an auxiliary port in your Google Home Mini.