• I've brought up a Windows 11 Enterprise trial VM and installed 3CX to it.
• I tried using my YeaLink T55A Teams phone in hybrid mode as a SIP phone but found this to be either not doable or feasible.
• Currently testing the softphones on PC and iPhone.
• Purchased DiDs and a SIP trunk.
  • The SIP trunk is up and running, according to the green light in the system.
  • I'm currently unable to call out of the system and troubleshooting what that is.
    • Appears to be a firewall PAT issue.  Despite having the machine in the router's 'DMZ' mode, things are still happening.  Yay.
• Really enjoying the ease of setup to this point.  In fact, it seems too easy compared to Cisco UCM, like I'm using a toy version of a system.  There's plenty of features included with 3CX at the moment, so once I get the calls working I will start messing around with some of those.

UPDATE:

• Resolved the audio issue by opening additional firewall ports.
• Able to call out using a dial-out number to specify external calling, as well as call in.
• Tested a brief auto attendant setup successfully.
• Next steps:
  • Looking at the different ways to connect a local desk phone to the cloud.  Thinking of bringing up an SBC, either on a Hyper-V Windows 11 Ent trial VM or a Raspberry Pi device.