I doubt (or just hopeless here) as looks like that hub you linked to uses VL100 (Power Delivery 2.0 up to 60 W) but I read that Librem 5 like to be served from PD3.0 specification source USB-C male connector and not from old type PD2.0 charging device (including hubs supporting PD2.0 pass-through):
Neither that unnecessary pumping of this Vava hub with 100W (although max. of 60W recommended) GaN charger will help there (as you described your usage scenario). But if original Librem 5 charger is used to power this hub you still might get max. of 19W on this hub PD2.0 male connector and this might turn out to be better option …, it is worth to be tried (I think, but not an expert).