Smash Bros Ultimate: Is Doc’s the only Gym in the game

Mii Fighters can be created directly in Smash Ultimate, which is handy since you can't create them on the Switch menu. Mii outfits are still collectable in Switch.

All custom moves have been removed with the exception of Mii Fighters which have the same custom moves as in Smash 4. Their custom moves are edited in the settings used to create Mii Fighters.

Spirits can be used in local multiplayer matches and the World of Light. They can add a larger variety of buffs, stats modifications, and even nerfs. They function somewhat similarly to stickers in Brawl but with a larger range of effects and they can be removed from a character without drawback (removing a sticker causes you to lose the sticker).

In addition to spirits is Dojo training. There are various Dojos obtained through playing the World of Light which each providing a range of stat modifications that can be applied to spirits, for example increased jump and weight but decreased speed and attack. One Dojo (Slowpoke) can remove other Dojo stat modifications.

Amiibos function similarly to Smash 4. Any amiibo for any of the playable characters, including those for Smash 4 and those not created for Smash, work in Smash Ultimate: a list of these amiibos is here. Certain amibos also grant you a spirit that corresponds to the amiibo, also contained in that list. Contrary to the rumours, amiibos don't unlock characters instantly.

Turning on airplane mode solves the issue, as the black screen occurs when connecting to wifi that has a weak signal.

You can turn wifi back on after you've got the game going!

Solution pulled from here and here