Has to be a different game from the last release, not just an DLC ...
Remasters, remakes do not count, such as Age of Empires Definitive Edition.
Spin-offs in this case would be releases from the same franchise, which do not use the same gameplay / format and are not continuations of the series, but are separate games in their own right ... For instance, a turn-based strategy game from the War craft franchise can be counted as such ...
Strategy games include real time, turn based, massive online multiplayer, digital collectible card game etc ...
Has to be released by happy new year 2029 ...
If you have suggestions feel free to add it as an answer ; i reserve my rights to remove it if i think it is unreasonable or duplicate and/or there are comments that make such case ...

Feel free to add options that seem reasonable and fit to the above description, if you have any questions > send DM or ask in comments ...

Flash games are of course not counted