I really want to record smb3 on my switch but don't know how to do it.Does anybody know how?

You can use a phone, or a camera to record. Many people do that with DS.

I have an elgato capture device for games on the Switch, but it is a little pricey. A phone or camera is the cost effective method (in my opinion).

Capture device for sure. I use this one which talks directly to OBS.

https://www.amazon.com/dp/B00BA4ILX8/ref=cm_sw_r_cp_apa_i_U09yDb5XXMD2A

thanks yall