Run Power Automate Workflow from a 3rd party call

I guess web connectors are on the outs. I have a Power Automate Workflow working that posts a message to a chat in teams but using same code I cannot post via a script on one of my servers. Authentication issue I suppose. So, how would I authenticate my code using an MS user and how can I do it without needing MFA.  Sorry, might be clear as mud but I what to send data to a Teams Chat using a Power Automate Workflow via a PHP script on a linux box.