I think there was an extension named Skip Redirect that solved this issue...
QuestionMark
Some websites display warnings even though everything works fine, like web.skype.com. But that's the closest thing to doesn't work I've ever seen on Firefox.
What about Apple's WebKit? Does it count?
If you might need to share anything to Windows devices (unlikely), Localsend is much better. Also I think Warpinator couldn't share text (maybe I just didn't see that option or it has been added), but Localsend can do that. But they're not that different.
I personally use KOReader for EBooks. You can download a dictionary on it and it'll tell you the meaning of any words you select. I suggest you give it a try. Oh, and if you wanted to read PDFs MJ PDF is great.
Maybe try delta.chat? I use it, and it's quite good. Just make sure the guaranteed end to end encryption thing is on.
Write. Anything you like. Nonsense, the issues of the world, a memory, a story. Sometimes, things (thoughts/memories) hurt less when written. Then you can burn the paper. Or tear it. Or do nothing with it. But burning it feels so good. It's like burning your sad thoughts.
Florisboard has an undo and a redo button.