It's true that Barcelona's current financial condition makes it difficult for them to sign star players. Although they were able to sign Gundogan for nothing, signing Mbappe, who commands a large transfer fee, would be a significant challenge.
I would never expect Barcelona to try to bring Kylian Mbappe into their squad when they are really in a financially tight spot. Barcelona can't compete for the star players available on the transfer market, it really makes it difficult for them to maneuver about that.
So for conclusion, I really believe that Kylian Mbappe is not a player who will play for Barcelona next season or in the next few seasons. Barcelona must solve their financial problems gradually, but it will never be easy.
There isn't much room on Barcelona's squad for new, pricey acquisitions because the team currently has 26 players, half of whom are foreigners. Transfer fees from players like Griezmann and Trincao don't come close to covering their current expenditures. While Real Madrid is a leading candidate to sign Mbappe, the issue is far from settled. The earlier new contract offer from PSG is an example of how a sudden change of heart can affect the outcome of transfer proceedings. The likelihood of Mbappe signing with Barcelona is, therefore, not zero
Barcelona has sold several players and made several agreements with several players regarding termination of contracts. They do all this to save expenses and reduce their responsibility in paying players' salaries, that is clearly not Barcelona's desire if they are not financially in trouble.