he would not be a qualifying child because he's over 19 (as of 12/31/2020) and not a full-time student in 2020.
however, he could be a qualifying relative (ie tax law parlance for being a dependent) if
1) his gross income for 2020 less than $4,300
2) you provide over ½ his support
3) isn’t a qualifying child of another taxpayer
4) does not file a joint return
so based on what you provided tests 1 and 2 are met. It seems likely that test 3 & 4 would also be met
if so you get to claim him as a dependent.
