In a video shared to TikTok, Alli could be seen working on his shooting at Barnet’s base.
Manager Dean Brennan has now invited the 30-year-old to join him for first-team training in a bid to improve his fitness.
Alli has been without a club since leaving Como in September 2025.
He made just one appearance for the Serie A outfit, having been sent off on his debut against AC Milan for a foul on Ruben Loftus-Cheek.
Could Alli join Barnet?
A return to English football could now be on the cards if Alli takes up Brennan’s offer.
The Bees boss spoke to Alan Brazil and Gabby Agbonlahor on Thursday’s talkSPORT Breakfast show.
Asked if Alli had been renting out the club’s facilities, he explained: “That’s exactly what he’s done. Our facilities are available to rent.
“We don’t live in Disneyland down at our level so our lads have to pay their bills, pay their mortgage and we don’t get 10,000, 20,000 (fans) a game. There’s only a couple thousand we get.