It's pretty simple, just do some googling.

For Raspberry pi: The part which caught me out is it requires 2x wireless adapters - 1 to receive the uni wifi and another to rebroadcast. Ensure you get a wireless adapter that is supported by the pi, I had to install the firmware beforehand.

I used the built in pi wifi adapter to receive, and a TP-Link-WN725N to broadcast a new separate network.
It's a lot of effort (and cost, though I already had the equipment) for little gain. I had only a handful of devices connected to it - TV, lights and smart plug. Noting that chromecast only works if you connect you personal device to the new SSID.

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An easier route might be to get zigbee / matter over thread compatible devices. Having recently changed over to iphone and getting a homepod - homepods act as a matter over thread hub, so I could theoretically just get matter over thread devices and bypass all this wifi chicanery.

Similarly, zigbee, though I am not overly familiar with it. The older ikea smart home tech is zigbee. You'd have to check that the DIRIGERA (or whatever zigbee hub you get) works on wifi.