Hi   !
You can try installing this add-on that will force-enable Reader View even if the icon is not displayed :

https://addons.mozilla.org/En-US/firefox/addon/activate-reader-view/

This addon adds a button to the toolbar. Clicking on it activates the Reader View feature even if the icon in the address bar is not present. Technically, this add-on prepends   “about:reader?url=”   to the current tab’s address.

Reader view only displays text on a web page in containers that meet conditions like a specific layout. There is a minimum character count for containing elements that show in Reading mode, so you may not see all the text if the page isn't designed to be used with reader mode.

• view-source:resource://gre/modules/reader/Readability.js

See also:

• Reader: https://addons.mozilla.org/firefox/addon/reader/

cor-el said

Reader view only displays text on a web page in containers that meet conditions like a specific layout. There is a minimum character count for containing elements that show in Reading mode, so you may not see all the text if the page isn't designed to be used with reader mode.

• view-source:resource://gre/modules/reader/Readability.js

See also:

• Reader: https://addons.mozilla.org/firefox/addon/reader/

@cor-el your suggested reader addon was ok, but Firefox inbuilt reader mode includes Text-to-Speech integration which I heavily rely on my short naps :). Thanks for your help.