I have a Samsung Galaxy Note 9 and my emojis have been showing up in text messages as question marks (???). If it's a group text they show up, but texting a person w/o T-mobile and/or with an iphone, they show up as questions marks.
For the longest I'd google and but could not find a fix. Today I googled and read an article that mentioned the different languages of text messages and phones, and it mentioned Unicode. It didn't tell me to change anything, I just remember Unicode being one of the options under text message settings. So:
(1) I opened up my test messages,
(2) selecting the 3-dots in the upper right corner of the screen,
(3) picked Settings,
(4) More Settings,
(5) Text Messages, and
(6) Input Mode. The options are GSM Alphabet, Unicode and Automatic. Mine was set to GSM and I switched to Unicode.
I then texted my daughter, who has an iphone, and it appears switching to Unicode as the "Input Mode" worked. I specifically texted only 1-person with an iphone because my emojis NEVER work when I text one person, only when in a group. My texting a series of random emojis came through as emojis and NO LONGER as question marks (???).
I really hope this helps someone who has had the same issue.
Take care.
Sherry