Sory to see this mate, unfortunately i’m looking to do the same, to use the ’ downloaded ’ pages as brave ’ let ’ me do and use them crossplatform but i seen some critical issues like yours and mine, that i can’t even open the saved page from the file manager.
Found some other ways to do keep texts and photos in form of pdf docs by printing the pages.
The simples way brave let us do ’ what we want freely ’ is to tell us to make bookmarks and or save pages but doesn’t let us to open them on phones from other devices and so on!
GOOD JOB BRAVE
Here is what i could find about any ways to save pages " offline "