I guess the new build has replaced squeekboard with phosh-os-stub. You can try squeekboard, I've placed a custom layout as well in kali builds, which is more compact than mobian's default keyboard layout.

I checked the build and the default keyboard app is phosh-osk-stub, you can install squeekboard.

There's only one issue with phosh-osk-stub, which is the keyboard layout; otherwise, it has more features than Squeekboard. Until I or the maintainers create a better layout for it, you can use Squeekboard.

visited https://gitlab.gnome.org/World/Phosh/squeekboard
this list of commands is better than theirs because i get the build dependencies as part of the whole setup.

git clone https://gitlab.gnome.org/World/Phosh/squeekboard.git
cd squeekboard
sudo apt-get build-dep .
mkdir _build
meson setup _build/
cd _build
ninja
ninja test
ninja install

the test is flawless and it seems to install, but i don't know how to run it. where is it? do i launch it from the console or find it in the gui?
their instructions on running it make no sense:

$ cd ../build/
$ src/squeekboard

the first command "cd ../build/" is invalid, and when i try to just "./squeekboard" from squeekboard/_build/src it gives a funny message like "maybe it's already running?"

p.s., the problem with the phosh keyboard is that it's in a grid, unlike a normal keyboard or most other virtual keyboards. so all the keys are in the wrong places.

cd /home/kali/squeekboard/_build/src
./squeekboard

** (squeekboard:19609): WARNING **: 17:07:39.303: DBus unavailable, unclear how to continue. Is Squeekboard already running?

FYI: i'm trying to get something similar to a gboard virtual keyboard (it has a dedicated number row and is packed with useful symbols after a long-press). and i customize my long-press down to about 200ms or something so it's fast. i don't ever use any automatic correction or suggestions. i use english, hebrew, and greek layouts, and find common latin accents within the long-press on an english keyboard.

Squeekboard can be installed through apt, no need to manually build. If you want a gboard-like keyboard, create one for you of just get phosh-osk-stub and make your own layout.

you're overestimating my abilities. i have now installed squeekboard through apt as well as manually building it. but i still don't have any idea how to run it or use it

for example, i have not found a place in settings where i get to select which virtual keyboard to use. and when i ran squeekboard it failed to load. am i supposed to kill the current keyboard first? what is the process to change keyboards?

You can switch the OSK by running the below command:
$ sudo update-alternatives --config Phosh-OSK

Then, choose Squeekboard by entering the selection number. Once done, reboot your device.

Closing at @shubhamvis98 request