Samsung devices with the model numbers SM-G975F, DS SM-G975F and SM-G975X have been spotted in a certification on the website of the Russian body ROSTEST. These numbers could well pertain to the Galaxy S10, and suggest that at least 2 variants of the upcoming flagship are undergoing official approval already.
https://www.notebookcheck.net/Samsung-Galaxy-S10-variants-reportedly-registered-with-Russian-authority.369256.0.html