If Henry still dies in 1422 then the Dukes of Bedford and Gloucester are next in line, and if they dont have heirs in OTL, then Edmund Mortimer is the first "yorkist" or better put non-Lancastrian, who would gain the throne providing he lives long enough. However if all these die without heirs as in OTL you may still get a civil war between York and the Beauforts of Somerset, depending on events leading up to the previous king's death.