The blocks generated by this mod don't have recipes for being placed directly into a furnace or blast furnace. If possible it would be nice to have these generate automatically for consistency.

The blocks generated by this mod have the proper convention tags added. Mods in theory should be using those in their blasting or smelting recipes, so this would not be an issue; some mods may not be doing that for whatever reason. I will look into possible solutions; I cannot bulk-add blasting/smelting recipes for the generated ores because not every such ore should have one, and determining whether to generate one is non-trivial in practice.

This ores missing furnace recipes for me are all vanilla ores. Those being Iron, Copper, Gold, Nether Gold, Quartz, Lapis, Diamond, Emerald, and Redstone. It looks like all the modded ores I have did correctly transfer over and work correctly, the vanilla ores are the only ones missing these recipes.

All the vanilla ores that are generated are added to the c:x_ores tag.

Also I'm on 1.20.1 so I'm using the 3.0.9 version of the mod if that matters.

Hmm, wacky. The vanilla ores I create are added to the various minecraft:iron_ores tags and company, which vanilla has for deepslate and normal ores. Could be that vanilla is not using those tags for the blasting recipes though? I'll take a look and try to get a fix out in the next version -- a new 1.20.1 version with some fixes and some more default configs will (hopefully) be out soon.