I got the bike for free so it’s not like I’m protecting an investment, but y’know I don’t wanna replace it, having it stolen would suck. They all seem hella expensive, I was thinking of just going to the hardware shop and buying a fucking big chain and padlock lol.
Chain and padlock is definitely the cheapest option, the local dollar store might even have one pre-wrapped and sold for bikes specifically so it won't scratch your frame. Mine does for ~$15.
They're harder than U-Locks to cut through anyway because they're hard to hold still for the angle grinder, just make sure you use one that's thick enough.
I use a motorcycle chain that I found abandoned and a truck padlock, never had a problem in 4 years. It's heavy though, at least 10lbs.