Can the SRAM Rival 1 rear derailleur be used with an 11-46T cassette?

With a 1x system, any practically sized chainring will work. Do you already own this derailleur?

I expect that you can probably get this to work with a 46T cassette, but my suggestion would be not to buy a new one with that intention.

Hacking bike parts is great fun, my hobby. But when you are buying something new you should buy it for its intended purpose. I expect you will be able to find a similar derailleur that is comparably priced that is rated for the 46T cog.

If you already own it, that is a different story. You might try to find a friend with a 11-46 cassette that you can tryout before buying one. They are pretty common. If you already have both parts, sure give it a try and let us know.

By coincidence, I just answered a similar question here. I describe two success stories with derailleurs working on cassettes that are a little bigger than they are supposed to be.

Having fitted a few of these, it works on some bikes better than others. I think this is to do with derailleur bolt drop distance. The derailleur can struggle shifting in and out of the 46.

I have had more success using these derailleurs on 11-46t 10sp cassettes with 10sp shifters where the margin for error is better.

The size of the front ring doesn't matter as long as the chain is the right length.