1. Give an incentive to one or more of the compiler core team... (hardware, A machine, or a financial compensation might work)
2. Wait till one of them bites....(there is a foundation)
3. It is not a popular platform (maybe yet), so that may put people off.
4. It is less of an effort than adding a complete new platform/cpu, but still not easy.
In principle FPC has a rather good code generator for Aarch64, but adding a full platform is not that easy.( toolchain, cross compilation, libraries, etc)
And since WSL2 is supported, you can already run full-speed FPC applications. I would start there...