Edit: I'm reading in the comments that FUTO is non-commercial, therefore it does not meet the OSI definition of open source (even though it does seem to provide code and allow for modification and redistribution). So keep that in mind while reading.

I've been using FUTO Keyboard and like it. It has swipe, voice annotation, undo/redo, clipboard manager, and it's fairly customizable.

It has some AI functions but I turn them off, aside from voice input, because typing becomes a bit laggy (on my old phone at least). You can import different language models for the AI and voice stuff. The voice input is pretty impressive. The swipe is okay, I think it will get better over time. They use their own non-Google dataset/library for swipe (which you can contribute to by swiping on their website keyboard).

It's still in alpha. I think it was started or funded by Louis Rossman as something to attempt a private, and offline equivalent of the Google Android keyboard.

It's impressive for being relatively new. I hope they continue to get funded and work on it.

If you like Florisboard but miss autocorrect, try FUTO keyboard. I'm surprised it is not more popular with how feature rich it is.

I've been using heliboard for more than a year without any issues. Only think I don't like is the lack of emoji search(?)

I've been down this rabbit hole and here's the haul from Wonderland:

Conventional:

• Heliboard - Has glide typing, but the available library is unstable and old. The most polished.

• Florisboard - Currently under heavy development, but what's there is more than usable and very well done.

• Unexpected Keyboard - I actually love this one, but as a Fold user I need some auto correct. Uses swipe motions on each key for symbols and punctuation.

Unconventional:

• Thumbkey - A 3x3 grid using taps and swipes to type. I flip flop between this and Heliboard atm. Has circular motions to input caps or numbers. MASSIVE amount of layouts, including language, programmer, writer and more. Easy layout switch key on the fly.

• Flickboard - Same setup as Thumbkey. This would be my go to ever since they added a landscape layout that smart switches on inner Fold screen, but there's no separate key height for it, so you have to deal with non-uniform on one screen which isn't easy to type on. Also has circular motion for caps. No numeric, but there's the option of having a small number column.

• 8vim - The only one of it's kind since 8pen died. I'm learning this one and it's great, but wonky on inner Fold screen. Its hard to explain, but you use circular motions around on X wheel to input whole words at a time letter by letter. Start center, drag out into a quadrant, rotate to get your letter, go back to center, without lifting go to your next quadrant for the next letter. When you're done and back on center, let go to insert space, or you can move out into a quadrant then lift to end without a space. Takes a lot of getting used to.

Fcitx5 for Chinese, and Flickboard for English. Honestly sad that there isn't a decent open-source keyboard for Japanese though.

Openboard (fdroid)

Could you specify wether these support physical keyboards? (showing only a toolbar when one is detected). I'm using the default proprietary Kika-keyboard on my device and it's not great. Microsoft Swiftkey works but is not perfect and not FLOSS.

After trying couple of keybords (mostly AnySoftKeyboard and TypeWise [proprietary]) I have settled on Unexpected Keyboard due to easy switch of keybords to get to japanese keyboard and tts button.

FlorisBoard

Heliboard which is an active fork of OpenBoard.