Hello, good day!
I'm Tilaga, Powerapps and SharePoint developer.
YES, message can be sent on powerapps using Flow. Please let me know if you would like to take it forward.
My technical skills are below:
◆ SharePoint 2010, 2013, o365
◆ PowerApps, Power Automate (MS Flow), Power BI
◆ JavaScript, ECMA script, Jquery, Ajax, Rest Api, HTML, CSS
◆ Infopath Form, Content editor, content query webpart.
I have gone through your requirement and I found my skills are exactly matches with your expectations. I would like to work on your project as i have relevant skills to complete your task on time.