There's a tiny patch mentioned in your second link that makes TCG work again on M1 Macs

https://bugs.launchpad.net/qemu/+bug/1914849/comments/3

  $ qemu-system-alpha -nographic
  PCI: 00:00:0 class 0300 id 1013:00b8
  PCI:   region 0: 10000000
  PCI:   region 1: 12000000
  PCI: 00:01:0 class 0200 id 8086:100e
  PCI:   region 0: 12020000
  PCI:   region 1: 0000c000
  PCI: 00:02:0 class 0101 id 1095:0646
  PCI:   region 0: 0000c040
  PCI:   region 1: 0000c048
  PCI:   region 3: 0000c04c
  >>>