Impossible to add virtual machine

I am using maas 3.1.0-10901-g.f1f8f1505 and lxd 5.1.
I made sure virtualisation was activated in my bios and kvm-ok is returning :
>> INFO: /dev/kvm exists
>> KVM acceleration can be used

I tried to add a VM using the CLI and the MAAS UI.

I am trying to create VMs in MAAS following this tutorial https://github.com/antongisli/maas-baremetal-k8s-tutorial/blob/main/maas-setup.sh but I encounter a problem when I run:
>> maas admin vm-host compose $VM_HOST_ID cores=8 memory=2048 architecture="amd64/generic" \
 storage="main:16(pool1)" hostname="juju-controller"
I got the message: "VM host does not support composability."

If I try to add a VM manually through the MAAS UI, I have the error message "Error: An architecture is required." (see screenshot attached)

To reproduce this behavior, run the commands below in the terminal (from https://github.com/antongisli/maas-baremetal-k8s-tutorial/blob/main/maas-setup.sh):

# lxd / maas issue. either upgrade lxd or maas to 3.1
sudo snap install --channel=latest/stable lxd
sudo snap refresh --channel=latest/stable lxd
sudo snap install jq
sudo snap install maas
sudo snap install maas-test-db
# clone the git repository
cd ~
git clone https://github.com/antongisli/maas-baremetal-k8s-tutorial.git
# get local interface name (this assumes a single default route is present)
export INTERFACE=$(ip route | grep default | cut -d ' ' -f 5)
export IP_ADDRESS=$(ip -4 addr show dev $INTERFACE | grep -oP '(?<=inet\s)\d+(\.\d+){3}')
sudo sed -i 's/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/' /etc/sysctl.conf
sudo sysctl -p
sudo iptables -t nat -A POSTROUTING -o $INTERFACE -j SNAT --to $IP_ADDRESS
# LXD init
sudo cat maas-baremetal-k8s-tutorial/lxd.conf | lxd init --preseed
# verify LXD network config
lxc network show lxdbr0
# Wait for LXD to be ready
lxd waitready
# Initialise MAAS
sudo maas init region+rack --database-uri maas-test-db:/// --maas-url http://${IP_ADDRESS}:5240/MAAS
sleep 15
# Create MAAS admin and grab API key
sudo maas createadmin --username admin --password admin --email admin
export APIKEY=$(sudo maas apikey --username admin)
# MAAS admin login
maas login admin 'http://localhost:5240/MAAS/' $APIKEY
# Configure MAAS networking (set gateways, vlans, DHCP on etc)
export SUBNET=10.10.10.0/24
export FABRIC_ID=$(maas admin subnet read "$SUBNET" | jq -r ".vlan.fabric_id")
export VLAN_TAG=$(maas admin subnet read "$SUBNET" | jq -r ".vlan.vid")
export PRIMARY_RACK=$(maas admin rack-controllers read | jq -r ".[] | .system_id")
maas admin subnet update $SUBNET gateway_ip=10.10.10.1
maas admin ipranges create type=dynamic start_ip=10.10.10.200 end_ip=10.10.10.254
maas admin vlan update $FABRIC_ID $VLAN_TAG dhcp_on=True primary_rack=$PRIMARY_RACK
maas admin maas set-config name=upstream_dns value=8.8.8.8
# Add LXD as a VM host for MAAS and capture the VM_HOST_ID
export VM_HOST_ID=$(maas admin vm-hosts create password=password type=lxd power_address=https://${IP_ADDRESS}:8443 \
 project=maas | jq '.id')
# allow high CPU oversubscription so all VMs can use all cores
maas admin vm-host update $VM_HOST_ID cpu_over_commit_ratio=4
# create tags for MAAS
maas admin tags create name=juju-controller comment='This tag should to machines that will be used as juju controllers'
maas admin tags create name=metal comment='This tag should to machines that will be used as bare metal'
### creating VMs for Juju controller and our "bare metal"
# add a VM for the juju controller with minimal memory
maas admin vm-host compose $VM_HOST_ID cores=8 memory=2048 architecture="amd64/generic" \
 storage="main:16(pool1)" hostname="juju-controller"
# get the system-id and tag the machine with "juju-controller"
export JUJU_SYSID=$(maas admin machines read | jq '.[]
| select(."hostname"=="juju-controller")
| .["system_id"]' | tr -d '"')
maas admin tag update-nodes "juju-controller" add=$JUJU_SYSID