Used flaxseed oil, 6 months later it's flaking and rusting. What would you recommend instead?

Canola oil is the Absolute best

Canola oil (also called rapeseed oil in many countries outside the US) is usually recommended. It’s what the cast iron manufacturer Lodge uses to season their skillets.

I may be in the minority but i don't care what oil I use, I just keep cooking in it. I have used them all.

Ended up buying a refined avocado oil, I'm hoping it really is that and not a mix

Found this guide which suggest avocado oil: https://theflattopking.com/best-oil-for-seasoning-cast-iron/

I'm having trouble finding refined avocado oil though, all I can find is cold-pressed/virgin.

I generally use Crisco, but that picture looks like maybe the oil was applied too thick? I get really good results with Avocado oil too. My process is to wipe the oil on with a clean cloth, and then try to wipe it completely clean. There will be a very thin layer still on the pan. I used to season in the oven at 500F, but I have lately had really good results on the range. I turn the burner up to high and let the pan heat until it is smoking, and let it smoke ~10 minutes. Once the pan is cool, I hit it with another thin coat of oil.