From Supergirl Special #1, December 2023. Scan by Daughter of Krypton.
The finish line banner is in Doyle Kryptonian and is written in the Doyle Kryptonian font:
To date, there have been three versions of the Kryptonian language used in Supergirl comic books.
Writing and language created by E. Nelson Bridwell and Al Turniansky: The 1970s-1980s comics books
An evolved language, complete but lost
A Kryptonian transliteration font was created by Georg Brewer for DC Direct products and for use in DC comic books. This font was also used in Smallville Supergirl, and other DC-based television shows. The 2000-2020 comic books
Transliteration Font
Bottle City of Kandor English/Kryptonian Transliteration Guide
Touch for full-size image
Freehand writing guide:
2020-current comic books
Kryptonian Language
Beginning in 2003, linguist Darren Doyle started a project to create a full-fledged, real and complete Kryptonian language and writing system. His Kryptonian language incorporated vocabulary and grammar from the earlier Bridwell/Turniansky system, and expanded the Brewer transliteration font for his newer complete Kryptonian language.
Doyle's (basically) fan-created language and writing system has now become canonical: His constructed spoken Kryptonian language was utilized by the creative team on the Supergirl live-action television series and spoken by actors on the show beginning in 2017 during season 3.His unique language and font have also been used in DC's Supergirl comics (see above).
For more information on Darren Doyle's Kryptonian Language Project, please visit kryptonian.info —this is now a canonical language and writing system!
In short, both the Brewer Kryptonian Transliteration/Substitution font and the Doyle Kryptonian Language are currently in use by DC. When you see Kryptonian, it could be transliterated English; or it could be Doyle Kryptonian. One way to tell us by discerning which of the different but similar font designs is being used.