Not sure we do.
Glenn - trash and has to go
TPJ - our best second rower but can also play lock (a troublesome position for us) and is somewhat suspect in defence
Piakura - our best prospect coming through... sounds like he's getting comfortable with ISC so a debut this year looks on the cards. Might still be ISC next year before starting in 2023... also noteworthy that Piakura can play left side
Riki - reasonable prospect coming through but could be more suited to the middle. Also need to remember his form at the start of the year starting in 2nd row
And that's pretty much it.
So if Glenn gets punted next year we'd be going into 2022 with basically 1 second rower in TPJ (who could be considered makeshift anyway) and 2 prospects (one of which has already been dropped this year).
I think we definitely need another one and Sua is a known NRL quality 2nd rower.