Esperanta Klavaro 4+

This is by far the best Esperanto keyboard I have found. Others work alright, but can't be accessed as a normal keyboard to be used anywhere I want; this one allows you to do that. The reason I leave off one star is because I think it would be better if, instead of moving four letters to the area normally reserved for numbers, you had it set up so I could hold down the c and have ĉ appear above it as an option. Many existing keyboards for natlangs allow for this, like English and Vietnamese. It would allow for slightly larger keys as the ones now are a bit small and I make more mistakes this way. It's hard to backspace too so I end up typing ĥĥĥĥĥĥĥ at the end of what I'm trying to fix. Lastly, it would be nice if other parts of it reacted to your current keyboard settings, so you could turn the suggestions and clicks off if you wanted. If these were changed, I would say this is the absolute best app you could use for Esperanto!

The only problem I have is that I click “ĥ” like 6 times before I’m able to click the backspace button. I think it would be beneficial to make the backspace key a tad bit larger. Other than that I see no issues

This keyboard sure made it easier to get into the Duolingo Esperanto course. Personally, I like the design choice, as on this keyboard, where are the diacritical letters are on separate and easily accessible keys. For learning, at least, I find this easier than press and hold.
I do wish the spaceto key would act as a directional touchpad, when pressed and held, as the space at does on the standard iOS keyboard. But maybe Apple doesn’t expose that feature to third-party keyboards?