As of writing, the full set of Pokémon allowable under Regulation Set F has not been released, though it is safe to assume that all Pokémon currently allowable under Regulation Set E will continue to be allow under regulation set F. Trainers may use any Pokémon numbered 001-398 in the Paldea Pokédex or numbers 001-200 in the Kitakami Pokédex that have been are caught, hatched, and obtained as gifts in either Pokémon Scarlet or Pokémon Violet, as well as Pokémon and Regional Forms from the following list that have been brought from Pokémon HOME. It is expected that, as with the current Regulation Set E and the release of The Teal Mask, the full list of eligible Pokémon should be available in roughly two weeks, shortly after the global release of The Indigo Disk.
Apart from the expected addition of new Pokémon, Regulation Set F is otherwise unaltered from the previous Regulation Set E. Pokémon may be entered at any level, but will be set to level 50 during matches. Pokémon may also be given Held Items, however no more than one copy of any item can be present on a player's team. All battles will be limited to 20 minutes total, including 7 minutes of time per player, with Turn Time and Preview Times of 45 and 90 seconds respectively.
The original announcement for Regulation Set E stated that this rules set would only continue through to the end of November, however this was revised to push the date back to January 2nd as of September 11th. It's not been explicitly stated why the end of Season 13 and the start of the new Regulation Set has again been pushed back another day, though presumably the developers are simply making sure they're able to take some time off over New Year's.