Years ago I replaced my IKEA TRÅDFRI gateway with a Rasbperry Pi with a Raspbee, running deCONZ. It allowed me to mix and match ZigBee devices from various brands and make flexible configurations. Plus the integration with Home Assistant is superb. However, one thing I lost is the ability for the IKEA remote to control my lights directly when the deCONZ gateway is down, which was possible back when I used the IKEA gateway.

If your Wi-Fi network is on channel 12 or 13, change the regulatory domain of your wireless networking driver to make the Raspberry PI 3B see it.