What I did to learn 6502 was start not on the NES, but on the Apple ][... seems like an odd choice, and it has some serious downsides, but there are a lot of resources on archive.org for finding beginner assembly resources. The Apple also has a built-in ROM monitor, which is kind of a pain to get used to, but it does help in early debugging since you're dropped right into it when your program crashes, and can look at memory and the like. There are plenty of emulators for it (I've heard the later Commodore machines like the Plus/4 and the 128 also have the ROM monitor)

Not sure I'd recommend that route 100%, but you might want to poke around some of the first few chapters of the books even if you don't write anything for the Apple.

Some more general purpose-resources:

• When I'm coding 6502 I always have this reference for quick lookup.
• The Nybbles and Bytes youtube channel just started a series "Nybbles and Mouse Bytes" for 6502 basics, definitely worth checking out, I hope she continues it (the main series is good too, she's making a Commodore 128 game)