As title says, this is how it works, this issue has existed since the first time I tried using OpenWRT (18.06), and still persists in the latest, 19.07.2 build.
When I am just setting up for the first time, I can't start using the 2.4 radio I've configured, unless I also configure and turn on the 5.0 radio, even if I'm not planning to use it. When I finally configure and turn on the 5.0 radio, the 2.4 becomes visible by devices, and they can connect to it (they can't connect to it even when trying to enter it manually). Curiously, at this point I can disable 5.0, and 2.4 keeps working; however, as soon as the router reboots, the issue returns, and I have to turn on the 5.0 radio once in order to start using the 2.4 one.
So, what could possibly be the issue? Is there any way to completely remove this dependency on the 5.0 module I'm not using at all?