I’ve been meaning for years to set up a solid archiving system that I don’t have to manually babysit. I’ve had my eye on mailpiler (https://www.mailpiler.org/), but haven’t found the time to get up to speed on it. I’m the meantime, I drag messages to a local folder like a barbarian.
Haven’t tried netbird, but I do like Tailscale and headscale. Last time I looked at all these, I landed on Netmaker, which might be worth a look. It’s WireGuard based and has a nice web ui for management.
Hey, as others have said, you can definitely set up OPNSense in a VM and it works great. I wanted to take a second and answer the first part of your question: it cannot run in Docker. Containers in Docker share their kernel with the Linux host machine. Since OPNSense isn’t a Linux distribution (it’s based on FreeBSD), it can’t make use of the shared Linux kernel.
There’s a pretty interesting series on the topic at Tall Paul Tech’s YouTube channel (here’s the most recent: https://youtu.be/WFso88w2SiM). He goes into quite a bit of detail over the course of a few videos about how he handled everything and highlights some of the trials and tribulations with the isp. It’s not a guide per se, but definitely stuff worth thinking through.
This is the route I’d go. I use FreePBX for all this, but my voip provider could do most of the work (voip.ms). There are decent softphone apps (Zoiper, Linphone, etc.) to initiate calls from and porting a number to the voip provider isn’t too difficult.