QEMU only supports the "legacy" interrupt controller, which should be equivalent to the ones in a RPi ≤ 3. So I put `enable_gic=0' in the config.txt and set up the "local timer" in the interrupt controller to fire repeatedly. This works for QEMU, but not on an actual RPi 4.
Mastodon is a server for a federated social network: everyone can run a server if they want to, including me. So this is a Mastodon server for me (Vierkantor) and my friends.