Dutch-MeshCore firmware before merge 32dd8ad (2026-10-19) does not
accept a scheme in mqtt1.server: it builds <proto>://<host>:<port> with
proto from the port alone, so mqtt://host became mqtt://mqtt://host:1883.
Reported by an observer operator on the live instance.
The mail now writes the bare host and adds a scheme only when the port
would pick the wrong one (for example TLS on 8884), which needs firmware
from 2026-10-19 or later.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>