Ever since my friends and I got halo 5 we have never been able to lobby or game chat without creating a party. I’ve reached out to Xbox support several times and they have sent us here. All our settings seem to be correct.
It’s best if you guys are playing as a fireteam to start party chat anyway. That way the chat only includes your party. You won’t be listening to 5 yr olds yelling and screaming. When I played fireteams with friends in my company we always started a party chat.
Halo 5 has never supported lobby chat. However, game chat has been a thing, so unless it is broken, it should be functioning. If you aren’t hearing any players in game chat, it could be because no one else is using it, or maybe your settings somehow are blocking it.
Last time I used game chat was awhile ago in a custom game, but it worked. Depending on your game type, you may not hear voices in game chat (like if you’re doing FFA).