No cap, there was a translation of Beowulf a few years ago that deadass translated the first word of the saga, "Hwæt", as "Bro!" (like how a drunk storyteller sitting next to you at the bar might say "Bro, listen to this shit" instead of the more staid/traditional openers like "Harken!")
I don't know if this is a reference to the recent South Park episode, but do teenagers really say "bruh" so much? I thought that was something people said a decade ago, although they used to ironically spell it "bra" sometimes.
The spelling change seems to be indicative of the generation shift (and a slightly different pronunciation). From what (little) exposure I've had to teenagers in recent years "bruh" is "correct" (and "bra" is "ancient" and "bro" is "boring"). Slang usage shifts in weird ways.
I'm sure both still exist. Slang always is prone to regionalisms and in-group markings. What I've heard (on Xbox voice chat primarily) as commonly used today is "bruh" like much closer to how most people pronounce "duh". I don't know where it originates dialectally other than "often heard in Fortnite and Minecraft".
(Definitely the one closer to my youth came closer to "bra"/"brah", and while some of that was assumed to be surfer-originated, I can't tell you how much it was related to Hawaiian pigdin or just convergent evolutionary vowel shifts.)
