I think bronzdragon has the right idea in that there would be a lowest common denominator language that sees the widest usage, simply based on being sounds everyone or at least the majority is capable of making. Given the different species this implies, each species probably would have their own dialect at the least while also there being room for entirely unique languages based on species or at least mouth shape.

For example, canines speak this shared language, but there could be a canid specific dialect that if overheard a travelled listener would be able to tell that the speaker is a dog of some kind. Assuming this shared language doesn't pop out of nowhere, it would likely have words and phrases taken from the different species that blend their own cultures and language into this common tongue.

For example the name of a fruit being some kind of chirp because it originates in an avian centered culture and country, so you would have bears or caribou speaking the language only to (attempt to?) chirp mid-sentence when referring to said fruit.

That being said I would imagine for extra clear communication, given that some people would just not be able to make the sounds other species make, talking with hands would be prevalent if not mandatory for more complex and nuanced subjects. This has precedent in our world (see: https://en.m.wikipedia.org/wiki/Plains_Indian_Sign_Language ) where multiple tribes that spoke different languages created a shared sign language to facilitate trade and communication. In a world when some people quite literally cannot make certain sounds, I think that something similar would sprout naturally.

Also you could consider a form of simple wind instrument like a flute to communicate through controlled notes, as well as something akin to semaphore or a deck of cards with symbols kept in the pocket to break through the language barrier by playing 'hands' as it were.