Very customizable (I like having number row always visible, and having long press for symbols on each letter).
Has gif support built in.
My biggest pain point is:
It auto corrects words that are spelled correctly to other words. I type "our" and it changes to "out", I recently typed "purpose" and it changed it to "purple". Autocorrect is awesome and necessary, but I hate that it corrects words to other words and not just typos. I wish I could find a keyboard that has the things I like without this annoyance.
How would you like to switch between them? I use 3 regularly with different layouts and I've never had an issue. For me, a keyboard swipe is quicker than a long press and tap to select, or a tap on a single button. It could be any of the above. You can also have the switching button in the top menu or by the space bar.
I don't think there is a free/private keyboard with gifs or stickers. There's gboard, SwiftKey, Samsung keyboard, and increasingly sketchy keyboards from there on down.
Oh, I meant free as in not proprietary. Free as in freedom.
I remember hearing about Fleksy keyboard years ago, although I can't really attest to it. It seems to have far fewer trackers than most proprietary keyboards, and just for analytics. Most other keyboards you find will send your data to advertisers or worse.
So far, most of the ones suggested here are free and private, meaning that they belong to the community and not to a company, and they do not collect or sell your data. That may be a factor for you or it may not, but I think a lot of people on Lemmy tend to care about it.