We moved all the User from Skype for Business on premise (with Enterprise Voice) to Teams (with direct routing). Now, what are the last steps to remove the Skype for Business on premise deployments (Front End Server / Edge Server)? I didn't find any article from Microsoft or any blog about it. What about the DNS-Entries (sip, federation…) which still point to the on premise deployment? Do I have to change it, or just delete it? Do I have to consider other things?
Maybe some logical next steps would be to turn off the servers running the Skype for Business Infrastructure and make sure no ill effects are seen. If everyone is now housed online I wouldn't think you will see any problems because they shouldn't be hitting any of the internal instance. Escalate from there if not further issues are seen decommission the DNS and server infrastructure. Maybe make a back up of federation settings (communicated to federated vendors that you've moved online?) and dial plans before fully decommissioning?