There are quite a few more. For example Debian, Ubuntu, Manjaro, Arch, Fedora, Alpine and Kali also have ARM ports (and probably many others too). Raspberry OS is purpose-built for ARM Desktop. There’s others too.

Asahi isn’t specifically an ARM Linux, but an Apple Silicon Linux.

Apple Silicon is ARM, but it’s also its own semi-custom thing that’s not directly compatible with other ARM stuff.

That’s the main issue with supporting ARM: You don’t have one platform like x86/x64.

On x86/x64 there’s an abstraction between the machine code language and the microcode that’s actually executed in the CPU. There’s a microcode translation layer in the CPU that translates one to the other, so x86/x64 chip designers have a lot of freedom when designing their actual CPU. The downside being that the translation layer consumes a little bit of performance.

There’s also the UEFI system and a ton of other things that keep the platform stable and standardized, so that you can run essentially the same software on a 15yo Intel CPU and a modern AMD.

ARM is much more diverse. Some run Devicetree, some don’t. There are also multiple different ARM architectures, and since they are customizable, there’s just so much variety.