Oh man, I just can't get away from Multiling O Keyboard

it's not open source, hasn't been updated for years (though the developer did update all the dictionaries for Android 14 recently) but its customization options just can't be beat.

I use swipe left and right for delete and space and auto-correct with a dictionary I've been adding to for years. It allows you to add custom emoticons and words, it has a тяαทรƒ๑я๓ functions to add ⓥⓐⓡⓘⓞⓤⓢ ＧＩᙏᘻＩᑥＫＳ to text... It has an option for swiping, too, though that's instead of the swiping for backspace and space. You can also edit which letters have what symbols above it.

Here's what my keyboard looks like. Notice the handy copy, paste, home, end, undo and redo buttons, too. Which are also completely customizable. Haven't found anything that truly does everything Multiling O does.

I do wish it was open-sourced though, if only so others could update it again...