Here is how the EuroLeague market bylaws have changed

The transfer rules in the EuroLeague are changing and this, it must be said, was not particularly publicised.

As stated in the Turkish Airlines EuroLeague Bylaws of the 2024-2025 season, Chapter 3 ‘Registrations of Teams’, Article 10, Paragraphs 6 and 7:

10.6 During the Regular Season, player additions to the team roster may
be made up to and including Round 27. For rounds where games are
in the calendar on Tuesday/Wednesday the deadline is Monday at
18:00 CET. For rounds where games are in the calendar on
Thursday/Friday the deadline is Wednesday at 18:00 CET.
These deadlines refer to the arrival of the documentation at the
Euroleague Basketball office.

10.7 During the same season, a player registered in the competition may
only transfer once to another EuroLeague club prior to Round 27 of
the Regular Season until Wednesday at 18:00 CET on the week of
the calendar date for the game in question, provided he was
deregistered prior to Round 18. Should the round be played on
Tuesday/Wednesday, the deadline will be Monday at 18:00 CET.

Thus, there are no longer the windows of the past. A player registered for a EuroLeague club, released before the 18th round, can sign for any other EuroLeague team. But he can only do so once. If released after the 18th round, however, he can no longer be used in the EuroLeague for the 2024-2025 season.