On release of 21.04, there is no ARM64 build of kodi - which means you cannot install Kodi on a raspberry pi.
What I have done is taken the sources available in the repository and rebuilt it specifically for ARM64.
In a terminal:
sudo add-apt-repository ppa:ubuntubudgie-dev/kodi sudo apt install kodi
Hopefully this will be resolved properly for 21.10 - until then - enjoy!