Can all Wifi emitters dynamically select frequencies? Or is specific hardware support needed?
DFS (Dynamic Frequency Selection) is not only a part of the hardware (well, firmware), it’s required, especially if certain 5GHz channels are used. If your router is dual-band it has DFS.

Note that DFS is only intended to avoid interfering with non-WiFi users of the 5GHz band, like Doppler radar. It’s a very limited agility mechanism specific to avoiding these other users. It’s very slow when it kicks in; basically the AP shuts down, switches to a new channel, and starts back up. It takes many seconds to complete.

DFS is not intended to avoid other Wi-Fi users; they’re supposed to coexist and share the channel.

At startup, an access point can (and does), scan for a quiet channel and select one. Or you can override this and manually select a channel by managing the AP. But this is a static selection; the link establishment overhead for 802.11 is fairly high so it’s not feasible for it be agile in real-time.