hey! The stock markets were changed pretty significantly - I used to rely on them to make money too, but I don't even check them anymore because they're not that profitable. I can't recall exactly what changes were made - I think the value of many stocks were dropped and the max %change each day might be lower? Someone else might be able to provide more insight on this.
I've found that, instead of stocks, some of the quests (ex. the squishy quest) can be good for making tu - i think some people make around 20m per day doing that - but it's a lot of grinding, and you'll have to invest a bit in having a bunch of squishies before you start seeing a lot of profit.
I think they might be clearing names from old/inactive accounts soon, so if you're able to snag a good one you could probably sell it for a couple hundred mil. The value of tu has also inflated a lot haha
I'm not super active on here anymore so I'm probably not the best person to speak about this - hopefully someone else can provide more information!