Hi @akshat-nmims
The best solution is you get your Marketplace's APIs developed. Then you give your Marketplace's APIs to the supplier and ask them to talk to their channel manager providers to do the connection.

Otherwise, you integrate the channel manager requested by your supplier to your Marketplace.
This method is not preferable as there can be a number of channel managers and to how many of them will you integrate.

And each integration will have some investment also.