Perhaps so, but I’ve run HA on a Raspberry Pi under Raspberry OS, HA OS on that Pi, and HA Supervisor on a PC using Debian and am currently running it on a PC under Linux Mint. All of these worked with little or no delay between HA start and device status updates.
HA OS on its own doesn’t behave that way, so that leaves Proxmox or perhaps your specific hardware. Can’t help you though. Haven’t tried HA in any kind of virtual environment.
Something’s wrong with your configuration. What hardware, OS and HA config are you running?
My HA install does not lose anything when restarted. All my wifi, Z-wave & Zigbee devices, various entities and thermostat come back in the same state as prior to restart. I’ve run HA Supervised on two HW platforms and 3 distros and they’ve all functioned this way.
Microsoft’s Windows 11 malware/spyware likely has something to do with it too.
I was using Z2M and found it had some weird, unresolvable device control quirks with a dimmer I’m using. Switched to ZHA and have had no problems at all.