This week i spend some time looking for an issue where we wanted to install SCOM 2019 agents using the push method from the SCOM console. The agent where in untursted domains so gateway servers are used.
These install where failing with error code 80040155.To be more precise:

Operation: Agent Install
Error Code: 80040155
Error Description: Interface not registered

The SCOM gateway logs two events on this issue:

Event 10603
The Operations Manager Server was unable to establish a DCOM connection with the MOMAgentInstaller service on computer [GATEWAYNAME FQDN] with specified account "[ACTION ACCOUNT]". This will cause failure to configure System Center - Operations Manager agent.

Operation: Agent Install
Error Code: 80040155
Error Description: Interface not registered

Event 10612
The Operations Manager Server failed to perform specified operation on computer [GATEWAYNAME FQDN].

Operation: Agent Install
Install account: [ACTION ACCOUNT]
Error Code: 80040155
Error Description: Interface not registered

The fix was quite simple. register the MOMAgentInstallerPS.dll on the gateway. (regsvr32 MOMAgentInstallerPS.dll)