Open HTML files in browser - SharePoint Online

Melissa Klug I had about 650 html and gif files in an old sharepoint folder (I think it was 2013 version) and it worked perfectly.  I linked a contents page to a landing page which anyone with a credentials could access.  Our IT people have discontinued that site and I am left struggling with this "new" Sharepoint.  I uploaded all of my files into a document library like I did the old one, but it won't access the images (unless I put the full path in which is absurd so instead of imgsrc="myimage.gif it now has to be imgsrc="https://MYSCHOOOL.sharepoint.com/sites/Testing123/Shared%20Documents/myimage.gif).  I also cannot navigate from page to page by clicking "next" which would load the page (like href="nextpage.html")  If I put  long file name in front of that, nothing happens.  It still does not work.

I have also tried changing the file extensions to aspx and that does not work either.  I need to keep using these files the way they are.  I cannot create a new page in share point for all of them.  They are all interconnected via a table of contents and it is too cumbersome to redirect all those links (even if it did work) and it is too cumbersome to have to rebuild all the pages.

What in the world changed?  Why can't this work like it used to????

Supposedly there is a way to change a setting from Strict to Permissive but nobody ever tells you where to find that setting.  I have been banging my head against a wall for six days now.  There just has to be a way forward.  I just can't believe microsoft would inflict so much pain on everyone.  If I do not fix this, my life is over.

I've run into this before and one fix that we came up with -- rename the file extensions from .htm or .html to .aspx.  The files will then open in the browser as you expect them to.