@Th3sAib0t well done getting it running. In combination what what @Spacer wrote (welcome to the forums, by the way!), I am wondering if it’s an issue where you guys are running both 2.4GHz and 5GHz networks together with the same SSID? I mean that alone doesn’t explain why it works fine under vanilla Debian. I have heard of similar issues before, but as another datapoint, I am running 2.4GHz and 5GHz WiFi here using the same SSID for both frequencies using Unifi access points and have no issues connecting Pi Zero devices.
If you’re able to get connected to the Pi Zero, either by connecting a monitor/keyboard/mouse, or via serial terminal, or even via using a wired ethernet adapter, there are definitely some things we can do to dig into why it’s not connecting. BalenaOS is using NetworkManager so we can use nmcli to do some debugging.
From a terminal connected to the host OS, nmcli d wifi list will perform a WiFi scan - it would be interesting to know if this scan shows the network you’re trying to connect to. For example if I run that scan here on a Pi Zero, I can see my SSID listed once on a 2.4GHz channel, but if I run that same command on a Pi 3B+ or balenaFin, I can see my SSID listed twice, once on a 2.4GHz channel and then again on a 5GHz one.
Then, if you want to force a connection, you can use nmcli d wifi connect <ssid> password <passkey>.
To view logs you can use journalctl -u NetworkManager.
Perhaps if you’re able to grab logs of a failed connection attempt it may reveal something that will help us further narrow down what the cause could be here. I hope this helps!