One UI 3.0 is Samsung's most up-to-date software upgrade at present, and is based on Android 11. It has been rolled out to a growing number of flagships, the S20 series among them. Now, this group includes the 5G version of the Galaxy Z Flip.
This new firmaware (F707BXXU1CTL6) is compatible with the global variant of the next-gen clamshell (SM-F707B). However, it has apparently only appeared as an update on its units in Samsung's AUT region (or Switzerland) as yet.
Then again, users of the same Galaxy Z Flip 5G variant in other regions may be able to download the upgrade and install it via a tool such as Samloader or Frija, rather than wait around for the official notification to show up in their market. In addition to the major software version change, the package also contains December 2020's Android security patch.