I've been using simply steel as a steel ingot standin while using the better furnaces reforged mod, and that mod has a platinum tier furnace upgrade after diamond furnaces. There aren't any "simply platinum" styled mods out there for 1.20.1 that also make sense to be post-diamond tier (there's one that has this name, but it's a gold variant and is last updated for 1.19.2).
My suggestion here, to match that better furnace reforge parity, is to create a new tier using similar logic as steel, only instead of processing iron with coal, it's nether quartz with some other item.
Quick suggestion to both speed up steel creation and to add in a new potential decoration block.
Block of Crude Iron - 3x3 Crude Iron craft, use for condensing. Also can be crafted with a Block of Coal (or Block of Charcoal if the player is using a mod with that item type) and a Block of Iron.
You can blast a Block of Crude Iron into a Block of Steel, with 9x the XP reward as the regular blasting recipe for a single crude iron.