It is not possible to output UTF-8 with Powershell (6+7).

Powershell-Plugin with pwsh 7.1:
Write-Host "UTF-8 Sign: ✅"                            >> UTF-8 Sign: �o.

Bash-Buildstep with pswh 7.1:
pwsh -command "Write-Host UTF-8 Sign: ✅" >> UTF-8 Sign: ✅

I only have a Windows Jenkins environment.
To get UTF-8 support on Windows you must start jenkins with
-Dfile.encoding=UTF8.

After that other plugins output UTF-8 correctly but not the Powershell plugin.