This has been said multiple times but I’ll repeat it, every time I hop on to play a bit of halo I can usually have fun until I start going for challenges, I absolutely despise when they force me to play gamemodes I don’t like. Not only that but BTB is my favorite mode and there’s almost no challenges for that. This also affects the “events” being able to progress the event only through ONE mode is horrible. I used to like fiesta, now I just can’t play it cause I was forced to play it and grind it multiple weeks, I hate Land Grab but guess what I have to play it cause I want a red color for my armor. Just please, everytime I play this game I gotta decide between playing to have fun or playing to progress my challenges, why can’t I do both at the same time.
Shouldn’t literally anything that doesn’t require a specific mode specified work for BTB? Get kills, earn assists, get kills with X weapon, get points in PvP, other stuff like that.
I cant think of many specifically but there’s plenty that work in it.
Yeah if it’s “kill enemy spartans” or “in PvP” it can be done in basically any mode. Bot Bootcamp doesn’t count if it specifically says “enemy Spartans” though. But BTB should absolutely work if a game mode isn’t specified on the challenge. I don’t think there’s any BTB specific challenges, actually, I’ve never seen one 
Theres one Ive seen, “Earn X points in BTB”, but it doesnt show up very often.
Of course, objective ones work for it though (kill enemies in a zone, capture a zone as long as it doesnt say land grab, protect/capture flags etc).