For the Brawl the minimum ilvl is 330
Item Scaling
For Battleground Blitz, the item level for equipped gear above 312 item level will scale to 472 (4 item levels below Dragonflight season 3 Honor gear), similar to how gear scaling currently works for other unranked modes. The scaling is limited to 312 and above to avoid potential issues with over-scaling stats on items from previous expansions.
Players will also need to be at a minimum item level of 330 to queue for the brawl.
Also note that Solo Shuffle in rated format has a minimum ilvl of 434 or 435, full honor is 437.