NetworkManager fails at boot with "Could not connect to D-Bus" on Linux Mint, leaving interfaces down

Symptom

On a Linux Mint system, the boot log records the error NetworkManager: Could not connect to D-Bus, after which wired interfaces stay disconnected and no Wi-Fi network is joined. The goal is to understand why the daemon fails to bind to D-Bus and how that failure affects the machine's exposure on the network.

Component and configuration

The affected component is the NetworkManager daemon, managed by the unit file /lib/systemd/system/network-manager.service. The unit appears to declare After=basic.target but no explicit ordering against dbus.service, which suggests a startup race where NetworkManager launches before the system bus is ready. Because Linux Mint ships with UFW inactive by default, a boot where NetworkManager fails may also leave the firewall state different from what the user assumes.

Uncertainty

It is unclear whether the error is purely cosmetic in some releases (with networking recovering later) or whether it consistently means interfaces remain unconfigured until NetworkManager is restarted. Behavior may also differ between editions and between graphical and headless setups.

Questions

• Does the missing After=dbus.service ordering fully explain this failure, or are there other documented causes?
• When this error occurs, does UFW remain inactive even if it was previously enabled, creating accidental public access?
• Which journal and nmcli outputs would confirm whether the failure is transient or persistent?