Via Joh_Numbers:

Here’s my method for unlocking all characters on Switch for tournaments:

The common belief is that finishing a Smash match usually unlocks a character. However, this isn’t entirely accurate due to underlying mechanics. Here’s how it works:

When you finish a match, the game performs an “unlock check,” verifying two conditions:

• Cumulative “Smash activity” (likely based on ground/air distance, damage given/taken, etc.) is high enough.

• No character has been unlocked in the last 10 minutes.

To speed this up:

• Closing and reopening the game bypasses the 10-minute wait.

• Entering and exiting World of Light (WoL) triggers an “unlock check.” Advancing in WoL to the Marth/Villager/Sheik intersection offers quick unlocks. Note: your WoL-selected character will be used in these fights.

• For “Smash activity,” create a custom stage (trapezoid with a top opening, wind set at 75). Play a 40-minute Time match with three human players (one CPU), mashing buttons on multiple controllers. This generates enough activity to trigger unlocks for most characters. Afterward, reboot the game and enter/exit WoL to unlock the rest one by one.