The following Tryout Duels have been announced for the upcoming weeks:
-30 Seconds
The turn time limit for this duel is only 30 seconds. This Tryout Duel will run from December 24th to December 28th.

-2026 LP
Both players only have 2026 LP in this Duel. This Tryout Duel will run from December 30th to January 3rd.

-UNDER-SR
For this event, you can only use cards that are either N, R, or SR rarity. The announcement notes that you can also use cards with alternative artwork (usually UR), providing their other rarity is SR or lower, such as Sky Striker Ace – Raye. This Tryout Duel will run from January 4th to January 8th.

All times are subjected to time zones, as usual.

As a side note, the list of cards with alternative artworks for the UNDER-SR Tryout Duel mentions Hu-Li the Jewel Mikanko, which is not present in Master Duel so far.