Products are built to be distributed in specific channels. Channels can’t be made to fit products (unless you own the channel).
Every channel is a growth loop. So, when you're building out channels, you're building out growth loops.
How Is Product-Channel Fit Measured?
You’ll know when you have product-channel fit, when one or a few channels are bringing a disproportionate amount of new signups, and your product features are optimized for those specific growth loops.