Fyi the Futo Keyboard is not open source. It is source availabile with a license that includes open source aspects but it limits modification and redistribution. Aka the keyboard more or less dies when futu stops maintaining it under the current license.

Full license https://gitlab.futo.org/keyboard/latinime/-/blob/master/LICENSE.md?ref_type=heads

Notwithstanding the above, you may not remove or obscure any functionality in the software related to payment to the Licensor in any copy you distribute to others.

You may not alter, remove, or obscure any licensing, copyright, or other notices of the Licensor in the software. Any use of the Licensor’s trademarks is subject to applicable law.