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.
Invidious currently works for me. I use this instance: https://inv.nadeko.net/