SharePoint Online Site not working in IE (Internet Explorer)

We have both SharePoint Online and SharePoint 2019 On-Prem. We require IE mode configured on our SharePoint 2019 On-Prem site because that way InfoPath Forms open just fine in InfoPath filler as required. When we try put the SharePoint Online URL on the list to open in IE mode, we cannot login to SharePoint Online at all using EDGE. We had heard that you can't open SharePoint online with IE, but now we can't even open SharePoint Online with EDGE in IE mode. I fear there is no way to move our 1000+ InfoPath forms to SharePoint Online (And please don't helpfully tell me that InfoPath is deprecated and suggest I rebuild all my InfoPath forms in Power Apps unless you would like to come work for me for free for oh, say, the next 2 years rebuilding 1000 complex InfoPath forms in Power Apps!)