React / Reactstrap Warning: Legacy context API has been detected within a strict-mode tree

I have this same warning, and I fixed it changing in the index.js file, the value of <React.StrictMode> to <React.Fragment>. Since this removes the warning, is not guaranteed that your can be bulletproof.

In the event that someone comes here on after searching the question and is looking for insight this is it.

React strap (at the time of this post) uses the react-transition-group things fade in and out and menus slide up and down. After amalgamating the info on this subject here and on Github they are currently updating the library. I have finished the coding of that component by ignoring the warning.

It did not impede this iteration of that component. Happy Coding.