I'm still learning about all this stuff. Please pardon me if I'm wrong.
I checked on Sammobile firmware. Saw the PDA n CSC are the same for HK (TGY) n Taiwan (BRI). I flash via Odin but my N20U still shows, BRI/ BRI, BRI/BRI.
Found in the XDA forum, someone used google phone to type in the IMEI thingy. So I tried n select TGY. After the phone reboot, Wolah! My N20U shows, TGY/TGY, TGY/BRI something like that.. Can't remember as I went back to my N10+. Still like the form factor of N10+.
It works for me as I get names instead of numbers appearing. Oso, the SPAM call thingy works after I changed the CSC code.