Simply install, boot, and run the /odc add command while holding the item you want other types of that item to convert to and you'll shortly be converting items in no time.
Example: hold a thermal expansion copper ingot and run /odc add. Now, all other types of copper (railcraft,ic2,etc) will be converted whenever you have them.
Conversion Config Format (for pack makers):
# to convert all items from a tag to a specific item (eg. forge:ores/iron=minecraft:iron_ore)
namespace:tag=modid:item
# to convert one specific item to another (eg. minecraft:diamond>minecraft:netherite_ingot)
modid:item>modid:item
This mod is also available on Modrinth at https://modrinth.com/mod/aodc
For those not installing via the CurseForge launcher, you will also need to install MDECore.