Until recently, the only established and typographically widely available way to uppercase an ß was SS, analogously for small caps.
Uppercase variants (ẞ) have only been slowly gaining traction in German in the last two decades and only have been allowed as an alternative by the official German spelling rules in 2017 (the spelling rules never mentioned small caps).
There are some fonts which support it, but as long as your aren’t using one of them¹, substituting ß with SS when uppercasing is your only orthographically and typographically valid choice.
Note that just leaving the ß as it is, i.e., a lowercase letter within all caps or small caps was never valid.
If you are submitting to an academic journal, I wouldn’t worry about it until you are at the proof stage, where you should check that they didn’t botch it and you may nudge them to use an uppercase ß instead of SS if their font of choice supports it.
Even if you use such a font, you have to jump through some hoops to get a decent automatic ß-to-ẞ substitution, the easiest arguably being using a LaTeX variant that can handle intelligent font features such as XeLaTeX.
¹ And right now, you aren’t. Computer Modern (LaTeX’s default font) does not have an uppercase or small-caps ß.