Dembele would be the de facto replacement for Diego Costa in the Atleti ranks and would provide cover in the squad.
As Marca reported earlier this month, the deal is a loan until the end of the season with the option to purchase for €33m for Los Rojiblancos.
Costa terminated his contract at Atleti at the end of last month so the club have been compiling data on his potential replacement with his wages now freed up in the squad.
French striker Dembele had netted an impressive 44 goals across his first full two seasons at Lyon – whom he joined from Celtic in 2018 – but has struggled this campaign, netting just once in 16 Ligue 1 appearances, of which just six have been from the start.
Joao Felix and Suarez remain the standout attacking players at the club but Dembele would add competition for places.