It’s most likely a Bluetooth remote, so 2.4 GHz like @Karosm said. I was just looking into it yesterday and found this post. It should be possible to connect to Home Assistant with ESPHome.
If you want to double check if it’s Bluetooth first, download a fan app like Fansmart Pro or something like that (there’s a million apps with similar names, just pick the most downloaded one), open it, turn off the power to your fan+light (at the wall switch or breaker), turn the power back on and within the first five seconds after restoring power, tell the app to establish a connection. It’ll make a short beep and you’ll be able to control the lamps with your phone.
Right after posting, I found this, which is probably even more interesting: