Great question — answering as the UphillTech team:
It is not a problem as long as They have the same URL and the total content is not vastly different Or different URLs with a canonical tag. Just in case, you should use or backend to detect if its a mobile or desktop and serve the appropriate footer, rather than having both of them in the HTML.
Full answer by Rohit Gupta: https://webmasters.stackexchange.com/a/144121 (CC BY-SA 4.0).
Need it done for your business? UphillTech.