These terms are used so interchangeably these days—some may argue it’s not even worth separating them out. However, the challenges for each are slightly different and a nuanced approach can change the type of impact PMM and your company can have. Here’s how I think about these:
I'm big on analogies (perhaps annoyingly so), so equate it to a concert: The Portfolio or Suite is like the band. It's the grouping of the products that you sell/come to see. The Ecosystem is like TicketMaster or StubHub. It's how you gain access to see the band/use the product if you're not walking up to the theater box office to buy a ticket. The Platform is like the stage, where the band is performing, it's connected into the sound system and lighting, and because of it, all attendees are enabled to see and enjoy.
In a business setting, I do often hear the term Platform used synonymously with Suite, which technically isn't wrong--because your Suite can be the thing that allows a customer to do more things. Though that somewhat implies that you're the only one in that space. Whether or not you have direct competitors, there is always going to be some other vendor out there trying to get the same budget from your customer, so I tend to try to not use the terms "platform" and "suite" interchangeably. As customer's are getting more and more technical, I see the term Platform being used to explain something different than the Suite. The Suite is the grouping, the Platform is the connective tissue that makes it all work together, and then there is the Ecosystem which is the path you can take to tap into that Suite.
Today, portfolio, platform, ecosystem and suite are used interchangeably depending on the use case or scenario. Every technology company wants to be a platform today that encompasses multiple products/services/offerings.