exit the game, click the gear next to diablo 4s play button, click settings, tic the ‘additional commands’ box, and type -regioneu (if normally on US) or -regionus (if normally on EU)
Chars are shared cross region, and regions are cross play, you lose no progress and can play with the same people.
Log in, play, enjoy.
WORKED, THANKS! Though note, on gear, click settings, then find the additional as mentioned.
Edited to include the omitted step. Ty for pointing that out.
+1. Thank you.
/20char
YW, you can use null elements, like < asdasdada > hi < / asdasdasd > (without spaces) to hit the 20 char with what looks like less than 20.
Worked for me as well, thanks a bunch
Worked 2nd attempt logged in. Thanks! <3
oooh… So the command lines work for D4! Very good info.
It may result in more latency, but if it works then that beats not playing at all.
Is it just
-regioneu
With no space etc and click done and not modify install?
Not work for me 
Some commands work, most do not. I can confirm certain region commands work, and -novoice.
First try got same no license error, restarted battle.net client and it worked.
Thanks OP!
Right now you are a god walking amongst mortals. Have fun!
restart battle.net and try the game again
Nope. Was I trolled? Or did the DDOS attacker read OP and adjust?
What is your default region?
I think it’s random can’t login again. It is what it is, I hope the people who managed to login don’t log out. 
Have fun, guys!
I think alot of people are all changing regions at once, give it a sec, let em stagger through the new region auth ques with increased latency, and soon we should all be able to get in.
If anyone is able to confirm what asias region code is, or pacific if there is one, for diablo 4, please let me know, ive tried like half a dozen and they def arent changing my regions, only eu/us have worked for me.
I just use < twentycharacters > (without the spaces if course) … that pads it out with 18 characters right there. 
any string if alphas work