MAML is an XML-based markup language developed by the Microsoft User Assistance Platform team to provide user assistance.
Among others, it is used in SCOM to format Knowledge articles.
Here is how to convert a MAML string to standard readable text.
$String=$Maml -replace '<\/?maml:.+?>',"`r`n"
Note:
When you copy/paste code from a web site, quotes and backticks are often replaced by graphically similar characters matching visually more to the character font. However, the ASCII character is not the same and Powershell will return an error. Be sure to replace them with genuine characters you type with your own keyboard.