SSH has no Host header

SSH lacks an HTTP-style Host header, making it impossible to route multiple VMs through a single shared IPv4 address the way HTTPS does. exe.dev solved this by maintaining a pool of IPv4 addresses and assigning each VM a unique IP per owner, then using the {user public key, IP} tuple to identify the target VM. This approach requires bespoke proxy and allocation software but enables uniform domain-based SSH access across many VMs.