Gary Schultz
Thank you for reaching out about "View in File Explorer"!
For customers who have taken a dependency on File Explorer, its use will continue to be supported until August 17, 2021. We recommend that rather than use the Open with Explorer command, a better option is to sync your SharePoint files or move or copy files in SharePoint.
Since SharePoint Open with Explorer uses ActiveX technology, it's only supported in Internet Explorer. Open with Explorer doesn't work in Windows with Microsoft Edge, Google Chrome, or Mozilla FireFox, or on the Mac platform.
The ActiveX control is only needed when you're working with files in Windows File Explorer. Once you're done with File Explorer, you can then use any supported browser with SharePoint.