You can save source quality using the Aloha browser (assuming android). Click on the pic, then I believe you should hold on the pic until a menu pops up to save it. That should get your source quality.
It's definitely easier on PC if that's possible. You can add the "Allow Right-Click" extension on Chrome (probably the same on FireFox). Click on the photo, then right-click to open in a new tab and save pic.
Aloha on mobile used to be my go to but it’s really glitchy at the moment. OF seems to have made it harder so it keeps saving the wrong images in the set, just completely random.