Where is your home-brew prefix located? Is it /opt/homebrew or /usr/local? If the latter then the likelihood is you’re using homebrew for x86_64. I’ve checked my own m1 Mac and the homebrew repository - the gdbm formula correctly has an arm64 bottle so you should get it if your homebrew is an arm64 build. gdbm installed fine for me, as did snapcraft.
I was able to install snapcraft after re-installing homebrew, but now I’m seeing a different issue when trying to run snapcraft login - Not able to run snapcraft login on mac m1
Multipass cannot start VMs on an M1 mac, currently. This is due to using xHyve as the provider, instead of QEMU. VirtualBox does not support the M1 mac at all. QEMU should AFAICT support starting a VM on an M1 mac, but I haven’t tried it. Alternatively if Multipass could target Parallels that would work, but the backend code doesn’t exist for that and it would also require Multipass users to be Parallels customers.
The reason xHyve is an issue is it targets an older Apple API that has been deprecated in Big Sur, so Multipass is waiting on them to fix up their support first.
I’ve downloaded the multipass build from that issue and installed it on my own m1 mac. While multipass seems to work, snapcraft is pulling images named snapcraft:$base_snap i.e. snapcraft:core20 et al, without any architecture specifics for arm64. This means that it is trying to launch an amd64 image on an arm64 cpu. So we need @sergiusens or @cjp256 to look into what is required for arm-based images for building there.