It's not just SNI that's the issue. Caddy also can't handle Host headers with trailing dots, where the spec explicitly states those should be handled. So while

It's not just SNI that's the issue. Caddy also can't handle Host headers with trailing dots, where the spec explicitly states those should be handled. So while the SNI error is clearly on browsers (and bugs have been already filed), the Host header issue is clearly on caddy (which caddy sees as wontfix)