SuperTokens is an open source authentication solution offering features like: Different types of login: Email / password, Passwordless (OTP or Magic link based).

SuperTokens.com

Yes, that is the obvious solution, and I was going to do that, when I discovered that there is a ThirdParty.Discord recipe in the Nodejs app
https://github.com/supertokens/supertokens-node/blob/c0f605208b83150d36879f62ba0709d0831db1d0/lib/ts/recipe/thirdparty/providers/discord.ts
It makes sense only if there is also a related recipe in the client. But there is no recipe in the client. It is at least weird, isn't it?

On the client side, you only need to render a button for the discord provider.

See https://supertokens.com/docs/thirdparty/common-customizations/sign-in-and-up/custom-providers