A place to put helpful docs.
https://discordjs.guide has nearly everything one could possibly want to know about DiscordJS.
It seems like only messages responding to interactions can be ephemeral, but you can still attach the ephemeral property and not break anything even if not responding to an interaction.
for discord.js v13 (and by extension, Discord API v8), intents are required on initialization.
List of intents can be found here: https://discord.com/developers/docs/topics/gateway#list-of-intents
discord.js intents class docs: https://discord.js.org/#/docs/main/stable/class/Intents
When responding to the slash commands, it looks like a reply is needed or else it will say the interaction failed?