My expectation is that the web server is returning 500 to everything; it's "working in Edge" only because Edge is still serving you a cached view from before the web application broke and started returning 500. And as soon as you CRTL-F5 refresh, Edge will show you the same failure. I get 500 from your web server in both Edge and Chrome, for what it's worth.
Anything else that was added before the failures began, like a style or extension? Or maybe something that was restored, if you're actually moving to a new host and restoring the database from a previous board?
Identifying the cause of the current 500 response will involve looking at the Apache error log. Where you find that depends on your hosting service; might be an "error_log" file in your web site's main directory, or might be something you can only see in your hosting account control panel.
Ultimately the log is going to tell you about some sort of PHP error, configuration issue, or inaccessible path that prevented the Apache server from being able to respond at all to the web page request. i.e. We're not talking about a phpBB-specific error log; the web server itself failed and gave a 500 error instead.