This add-on has been great. My one concern is that I am unable to change the font using an Android phone and tablet. I've been trying to change the used font from the default to Times New Roman. The changes take effect on the desktop-based add-ons, but my one reservation is Android. Overall, amazing app.

Very good.

Like this and seems like potential addons. The problem is when i go to some news portal, the image size did not fit my screen. The image are the summary of the news.

Does the job and works reliably. Easy to use - click on icon to enter and exit. No 3-finger salutes on the keyboard or getting stuck in reader mode requiring a total refresh of the page.
Operation is MUCH more predictable than the "more popular" reader that's just named "Reader" for FF57+ (which also appears to collect usage data).
All that said, I like the "Enjoy Reading" add-on for the PaleMoon browser a bit better, but give this a try for FF57+. YMMV