Well since it’s a an app, installed to peoples computers, are are stuck using implicit auth, so as you don’t leak/release your Client Secret.
But it depends really on which endpoints of Twitch you need to call for your Application, it’s probably way easier to make your app connect to your server, logs into your server, (steam/oculus device ID auth whatever), and fetches the existing YOURSYSTEM/Twitch Account link and uses the server to proxy the requests.
Then you can authenticate between your app and your server however you want.
Thats how, say, Doom Eternal knows my TwitchID, Doom logs into my Bethesda account, via my Steam account, and can talk to my accounts linked to my Bethesda account, where it logged in via my Steam account to start with.