Are your plugins etc up to date? I had a similar issue and updating plugins seemed to fix it. YMMV.

I run a number of Shelly devices on an iOT vlan with opnsense, but I used the integration- could that be an option?

I found a couple of the shelly devices (the humidity & temperature sensor and the smoke alarm) needed to be able to access HA to send updates so I created an opnsense alias to allow them just to access the ip it’s on. I could see MQTT being useful for these maybe?

I also have a couple of plugs and plus 1pm’s that just sit isolated on the vlan and get accessed by HA from the LAN. The integration was super easy to setup for these.

But this post didn’t suggest Docker, it suggested a VM. This would be a totally sensible thing to do as you can just recreate it if you mess it up. Virtualbox works fine on Windows and Linux. Install it and spin up a distro.

Mate, the suggestions you have been given for VMs and docker are to help you recover easily should you mess up. If you are going to moan about that…maybe just install bare metal and get on with it yourself?

I have two window units and a switch on the wall wired in to turn power on and off to them like yours. It would be the same as pulling the plug. I added a Shelly relay to each of them to turn them on and off via home assistant.

I can’t change any settings on them as they are physical dials on the front of the unit. However, I generally keep the dials the same and just turn them on and off with the relays.

There’s a warning not to turn the units off and then back on in 3 minutes (I’ve seen this on quite a few units), but I think lots of units only enable the fan if they are switched on in that time frame as a precaution. The compressor comes on after the warning period passes. No idea why.

I use a Broadlink RM4 for exactly this! Works great once set up. Had to let it connect to the internet to set up the first time, then blocked it on my iOT vlan so only Home assistant can talk to it. Has worked without any intervention for several years.