According to All Market, Liverpool are interested in Como midfielder Maximo Perrone and regard him as one of the potential replacements for Mac Allister.

Mac Allister is considered very likely to leave next summer. Born in 2003, Perrone is an Argentine midfielder under Fabregas.
In addition to Perrone, Liverpool are also monitoring three players with similar characteristics to Mac Allister: Real Madrid's Aurelien Tchouameni, Brighton's Yasin Ayari, and Everton's James Garner. Chelsea and Aston Villa are also following Garner.