Not much help but it seems like the complexity of maintaining the packages is too daunting … Only building kernels is currently supported. Support for cross-building user space programs is not currently provided as that would massively multiply the number of packages.
I scp my projects to the aarch64 machine and build the RPMs there. It’s slowish but is a possible solution (although probably not what you were looking for).
$ dnf info gcc-arm-linux-gnu-11.2.1-1.fc35.x86_64
Last metadata expiration check: 0:00:16 ago on Sat 06 Nov 2021 12:18:28 PM EDT.
Available Packages
Name : gcc-arm-linux-gnu
Version : 11.2.1
Release : 1.fc35
Architecture : x86_64
Size : 26 M
Source : cross-gcc-11.2.1-1.fc35.src.rpm
Repository : fedora
Summary : Cross-build binary utilities for arm-linux-gnu
URL : http://gcc.gnu.org
License : GPLv3+ and GPLv3+ with exceptions and GPLv2+ with exceptions and LGPLv2+ and BSD
Description : Cross-build GNU C compiler.
:
: Only building kernels is currently supported. Support for cross-building
: user space programs is not currently provided as that would massively multiply
: the number of packages.