as part of the compatibility updates HUD API will use the value REPENTANCE to check if the player is running the repentance dlc, you can use this in a simple if statement to add alternative code


HUDs will need to be updated to replace instances of player.SecondaryActiveItem to be compatible

here are examples of how the default huds were updated:
replaced "local activeitem2 = player.SecondaryActiveItem.Item" with
"local activeitem2 = 0
if REPENTANCE then
activeitem2 = player:GetActiveItem(1)
else
activeitem2 = player.SecondaryActiveItem.Item
end"

replaced "if player.SecondaryActiveItem.Charge == nil then" with
"if (REPENTANCE and player:GetActiveCharge(1) == nil) or (REPENTANCE == false and player.SecondaryActiveItem.Charge == nil) then"

replaced "local charges = player.SecondaryActiveItem.Charge + player.SecondaryActiveItem.BatteryCharge" with
"local charges = 0
if REPENTANCE then
charges = player:GetActiveCharge(1) + player:GetBatteryCharge(1)
else
charges = player.SecondaryActiveItem.Charge + player.SecondaryActiveItem.BatteryCharge
end"

replaced "local itemcharge = Isaac.GetItemConfig():GetCollectible(player.SecondaryActiveItem.Item).MaxCharges" with
"local itemcharge = Isaac.GetItemConfig():GetCollectible(activeitem2).MaxCharges"