Weapons teaching Lore skills?

Awesome. Yes, that's exactly how I'm doing it. I'm using your "cursed tweak" code to implement the upgrades. It's a simple system of 5 levels for 2 weapons. Would it be possible to have the character learn different Lores with each different upgrade?

Yes you could do with with a lore table for each character.

That's good to know. So I could have the weapons upgraded with the cursed tweak, then talking to a specific NPC who runs a check of my equipment... then if I have the required weapon, she gives me the respective Lores. Would that work?

Yes, with a one byte parameter you can allow lore (spell) X to be learned or lore "0" to "7" (with a lore table of 8 spell entries) at the same time if you check individual bits. It depends how you do it and what you need.