You can use an existing Github, Google, ORCID or possibly an institutional account to authenticate. Follow the steps below. It should take less than 5 mins.
After you submit this you’ll be sent an email to the email address you entered in step 5. Open this email and press the confirmation link.
You can now attempt to log in again using the same Github, Google, ORCID etc that you used before. When asked you should press “remember my descision” and then “Allow”. When presented with a list of teams select "Bluesky"
If you like you can install a desktop or mobile client. from this link
You will need the HZDR mattermost URL: https://mattermost.hzdr.de/. Make sure you also enter a "display name"