Blizzard are reminding players that this is the last week severs will be actually playable, with only the character selection screen being available starting with the next reset.
SoM (Source)
With weekly maintenance today, February 14, 2023, we are beginning the closure of Season of Mastery realms.
With weekly maintenance next week (Tuesday, February 21 in this region), all Season of Mastery realms will become available for your character list only. Characters will no longer be able to enter the game world itself at all.
After that time, you will still be able to access the character selection screen on your Season of Mastery realm and initiate free transfers to Classic Era or Wrath of the Lich King Classic via the Free Character Transfer option in the Shop Menu.
If you have not yet done so, you must log in and clear your mailbox and end any auctions you may have before February 21. You must also disband your guild if you are a guild leader. Free Character Transfers cannot be performed on characters that have active auctions, mail, or are guild leaders.
Season of Mastery realms will be available in this state for at least 3 months to allow anyone who wishes to transfer their characters the opportunity to do so before the characters become unavailable permanently.
We strongly encourage you to take advantage of Free Character Transfers within the next seven days, while you still have the ability to enter the game world.
Thank you very much for participating in Season of Mastery!