# bring the link up
sudo ip link set enp0s1 up

# give yourself an address in QEMU's usernet
sudo ip addr add 10.0.2.15/24 dev enp0s1

# default gateway for slirp
sudo ip route add default via 10.0.2.2

# DNS via slirp (or use 1.1.1.1 if you prefer)
echo "nameserver 10.0.2.3" | sudo tee /etc/resolv.conf > /dev/null

# sanity checks
ip -4 a show enp0s1
ping -c2 10.0.2.2
ping -c2 deb.debian.org