How do I stop my cats from hunting?

I have 2 cats that are indoor/outdoor. They both are avid hunters and are constantly leaving dead rats and birds on my door step. I talked to a few people and read some posts online but wanted to get some advice on how to reduce their hunting and/or stop it all together. I have tried the following with little success:

Switch them to a raw diet. The idea behind this is that the cats have a blood lust for raw meat and this will help take care of that need.

Put a bell on their collars so they can't sneak up on their prey.

Feed then 1.5x the amount of food they are used to so they become lethargic and/or don't feel the need to hunt.

As I mentioned, none of these things worked so I think I need to take more drastic steps, which include:

Convert them to 100% indoor cats. I feel like this is tough because I live in a 419 sq. ft guest house so likely not an option.

De-fang and/or declaw. I live in CA so I think this may be illegal but would need to do additional research.

Neuter them. They are currently not fixed so they spray a lot and like to fight other cats. I heard this reduces their rage and killer instinct.

Please let me know if you guys have any suggestions.