I have started with the preparations of the next Linux Mint Debian Edition arm 64. It is called Gigi and has version number 7. I was able to build a live system with LXDE in this case as it builds fast and the right base-files package. As you can see, it is real Linux Mint Debian Edition (LMDE) now, as recognized by fastfetch.
Edit 20 September 2025
Linux Mint Debian Edition 7 Beta has been released and I am up to date with the changes. When a stable version is released, the arm64 version will follow suit soon thereafter.