SfB 2019 Install Help

Hey everyone!

Happy Monday! I'm trying to install a handful of on-prem Skype for Business 2019 into a lab environment and I'm falling at the second hurdle when running 'Setup or Remove SfB Server Components'. I'm getting the error: 'Error 0x8007054b (The specified domain either does not exist or could not be contacted) setting launch conditions on DCOM layer during action SetDCOMSecurityEx.
CustomAction CA_SetDCOMSecurity returned actual error code 1603 (note this may not be 100% accurate if translation happened inside sandbox)

Error returned while installing Server.msi(Feature_Server, Feature_HealthAgent), code 1603. Error Message: A fatal error occurred during installation.'

All of the servers are part of the same domain. I can log into the skype servers with a domain account, DNs all seems to be working, nltest commands seem to come back normal.

Things that I've tried:

- Adjusting the COM Security settings for launch and Activation Permission to include RTCUniversalServerAdmins and my admin account to allow local/remote launch, and local/remote activation

- Setting a group policy to allow the group EVERYONE to make remote SAM calls (this seemed to have a broken a lot so reverted... I saw it on an MS forum that fixed it for someone)

- Run the installer as admin, run it w/out admin

- Put the server into a 'staging' area in AD with no policies applied.

Fortunately this same error is happening on all servers, which implies that there is a policy, registry key or some permission that's getting in the way.

Does anyone have any ideas of some other things that I can try?

Thank you!

Edit: I know Skype 2019 is old, I know I should be using something else. I'll be moving to Skype SE in Oct.