I've backported a few patches for AArch64 shim and done some basic tests. I'm planning to disable the signature check for AArch64 shim in the spec file until we get a real workable signature. On the other hand, Tumbleweed currently uses the shim-leap package which is directly copied from Leap. Since AArch64 shim doesn't exist in the current Leap, it cannot provides AArch64 shim for Tumbleweed. Will try to figure out a solution for that.