Source: https://twitter.com/FabrizioRomano/status/1804056911773392900
Nico Williams' release clause is 58 million euros and currently quite a lot of teams are interested in signing him. But the loudest rumors are from Barcelona who have been monitoring this player for so long and I think with their financial constraints it will be very difficult to sign him. Apart from that, I once heard an interview with Lamine Yamal who said that he would be very happy if he could play with Nico Williams at Barcelona.
On the other hand, the president of Athletic Bilbao responded to the rumors in a relaxed manner and he added that there was no need to worry about these rumors and he also said that Nico Wlliams was very happy at Athletic Bilbao. But I think everything could change if a club dares to redeem this clause and it is not impossible that management will release it.
Nonetheless, it is entirely up to the player; William may still leave Bilbao due to a personal request. Nico Williams' contract is about to expire, but there is no word on whether he and Bilbao are in talks to extend it. As far as I know, Bilbao has offered him a three-year contract extension, but Williams has not responded.
Barcelona could still sign him during the next summer transfer season. Nico Williams has very good relationships with some of Barcelona's players on the Spanish national team, so he still has a chance to join Barcelona.