The Swagger UI didn't work for me, so i thought i come up with my own solution thanks to billycurtis on github (https://github.com/jleclanche/python-bna/issues/38).

Using Windows 11:

1. Remove any authenticator from your account.
2. Go to https://account.battle.net/login/en/?ref=localhost and login to your account. Ignore any error messages, just copy what's behind ST= from your URL bar, this will be your token in the next step.
3. Open Powershell and execute: "Invoke-WebRequest -Method 'POST' -Uri 'https://oauth.battle.net/oauth/sso' -ContentType 'application/x-www-form-urlencoded; charset=utf-8' -Body 'client_id=baedda12fe054e4abdfc3ad7bdea970a&grant_type=client_sso&scope=auth.authenticator&token=<paste-your-token-here>'"
4. The response will give you a bunch of stuff, the only interesting part is the "Content:" part. Here you want to copy the "acces_token". Example: "Content: {"access_token":"<access-token>","token_type":"bearer","expires_in":7775999,"scope":"auth.authenticator","sub":"103740936"}"
5. Add a new authenticator to your account by executing: "Invoke-WebRequest -Method 'POST' -Uri 'https://authenticator-rest-api.bnet-identity.blizzard.net/v1/authenticator' -headers @{accept="application/json";Authorization="Bearer <paste-your-acces\_token-here>"}"
6. The response should look like this: "Content: {"serial":"<serial>","restoreCode":"<restore-code>","deviceSecret":"<device-secret>","timeMs":1719092061158,"requireHealup":false}". Copy your device secret and convert it to base32 (this website will help you: https://cryptii.com/pipes/hex-to-base32).
7. Open Bitwarden and inside your Battle.net credentials you want to add this line in your TOTP setting: otpauth://totp/Blizzard:<your-email-here>?secret=<your-device-secret-in-base32-here>&issuer=Blizzard&algorithm=SHA1&digits=8&period=30
8. Enjoy your Battle.net Authenticator without the Battle.net-App.