Abstract: Microsoft released Powershell 5.0 (included in the Windows Management Framework; WMF) but it isn´t supported (yet) on any Microsoft Exchange server.
So if you check the Microsoft Exchange Support matrix here, you can see that for example Microsoft Exchange 2016 supports only Powershell / Windows Management Framework 4.0 and not the version 5.0.
If you wish to find out which powershell version is currently installed use:
Inside a powershell command prompt.
Exchange 2016 & 2019 servers support the version of PowerShell that´s included in the release of Windows Server where Exchange is installed (see here or here). As Windows Server 2016 (for Exchange 2016 CU3 or later) and Windows server 2019 (for Exchange 2019) is supported now, which both have a build in WMF (= Windows Management Framework) version 5.x, it would be ok to use Powershell 5 with Exchange, but only on the mentioned OS types. Its still not supported to install versions of Windows Management Framework that are made available as stand-alone downloads on other operation systems. Additional keep noted that WMF 5.0 is outdated and is already replaced by WMF 5.1 which comes with Windows updates to the server OS types in charge (see here and here).