It just isn't an option. I've seen those how-tos as well, but they don't apply to my particular TV. I go into settings, and there is no option to manipulate the existing apps that are available to me. The apps just have randomly become available over the years. When I first got the set, there was no Hulu or Disney+ app on the screen when I would press Contour on the remote, then navigate to the Apps. Then one day, those two were suddenly available. The remote that came with my TV has buttons for Netflix, Vudu and Youtube, so my guess is it's an agreement between Philips and streaming providers on what apps are available and when. I don't know, I find it odd but it is what it is.
I don't understand if we're talking about the TV and you reference pressing the Contour button. The TV has its own operating system and apps and Contour has its operating system and apps. Two different platforms. The Contour box wouldn't have anything to do with steaming an app on the TV set. You'll need to use the TV remote to navigate the TV apps.
When I use the remote for the TV and go to it's apps, there is only a limited selection, and none of them are the ones I subscribe to. My TV is hooked up to the Contour box so that I can access Cox Cable. I have HBOMax and Netflix through Cox, but I also have Hulu, Disney+, and Prime Video and can access them with the Cox remote. I know it doesn't make sense, but I've spent countless hours looking for a way to manipulate the apps on my TV and it can't be done. It came with something called Net TV where the apps are found, and it just has a bunch of weird ones like Field and Stream, Popular Science, iFoodTV, Outdoor Life. Right now, NONE of my apps are working, so I will have to waste time exchanging this stupid Contour Box.
Yeah...being unable to steam via Control seems to be spreading like a virus.
I read the User Manual for your Philips 55PFL5601/F7, and it appears this online system you had previously noted is Net TV and Net TV controls its apps. Here's a copy-and-paste...
Net TV Net TV offers internet services for your TV. Use the TV remote control to browse the Net TV pages. You can play movies, listen to music and much more, all from your TV screen. – Because Net TV is an online system, it can be modified over time to better serve its purpose. – Some Net TV services can be added, changed or stopped after some time. – You cannot download and save files or install plug-ins.
Meaning, Net TV controls the weird stuff you can stream. This feature reminds me of a quote of Henry Ford, "Any customer can have a car painted any color that he wants so long as it's black."
I suspect those buttons for Netflix, Vudu and Youtube on the Philips remote are launching Net TV.
I'd take another look at those how-to articles to download apps onto your Philips. These articles may be instructing how to download and use apps outside of Net TV. Of course, this won't solve your problem with streaming via Contour, but the crux of your problem may be streaming via Contour.
I just checked all of my 3rd party apps and they are now launching and working. I see others with this issue, and someone said they had called and Cox wasn't even aware of it. I did a little research last night and saw that some earlier Philips TVs (pre-2017) will not allow for the manipulation of preset apps, and will not allow for downloading of any app stores (Google Play being the main one mentioned for Philips). I honestly don't know how old my set is. My parents bought it, and it sat at their house for a few years before they gave it to me, but it's most likey 2015 or so. So I guess I'm just stuck with the Net TV apps or the BS I deal with on Cox/Contour. Thank you for the article though, I'll see if there is anything I can do.