The game normally has a 10-minute cooldown between new challenger appearances. You can skip this on Yuzu to unlock the roster in about 2 hours.
If you prefer to "earn" them but want to move as fast as possible, you can exploit the game's challenger logic: super smash bros ultimate unlock all characters yuzu repack
In your game list, right-click on . Select Open Save Data Location . The game normally has a 10-minute cooldown between
file with a downloaded 100% save file found on community sites like Use a Save Editor : Tools like Ultimate Smasher Select Open Save Data Location
Complete Guide to Unlocking All Characters in Super Smash Bros. Ultimate on Yuzu Repacks
However, for PC gamers using the (an emulated version of the Switch game via the now-discontinued Yuzu emulator), the initial euphoria of playing Mario vs. Sephiroth wears off quickly when you realize the roster is locked.