I think this is more so an issue with kernel modules not being included. I had this issue on Linux Mint because a new kernel I upgraded to DID NOT have the "extra" modules and part of that reason is also because older kernels are named differently than new ones.
Take this example article below that shows it in action.
If you were previously able to type your password and a subsequent kernel update broke things here is the solution
Solution 1 - Install the "extra" kernel modules
Basically make sure that for your linux kernel that you have the "extra" or "modules-extra" additional kernel package installed if you have the problem that you cannot type your password at Boot to unlock LUKS.
The article above will show you what you need to do and this has resolved all of my issues with being unable to type my LUKS password at boot by adding the extra kernel modules. I also found until i did this even my NIC did not work so really, I think all modules should be built into the kernel by default or the extras should be a depenency.
Solution 2 - grub quietboot option
In the kernel line in grub you could change "quiet" to "quietboot". This will allow you to type the password.
I find this is not practical since often if you are lacking the modules to type your password, I found my NIC card didn't work too.
Solution 3 - hit Esc
Some report that hitting the Escape key will allow you to enter the password. But once again I found for myself that you are probably going to have issues if other kernel modules for your device such as NIC are still missing.
Solution 4 - are you using nvidia?
With nvidia drivers everything breaks and there is no "normal fix" as it is a longstanding known bug with nvidia.
The permanent fix is to add the following here:
For some people you can keep splash and just add "nomodeset" and it will be OK as well.
If booting on the fly by holding shift or Esc to get the GRUB menu edit the kernel line and remove "splash" and you should be able to boot.