SamyGO

no GAMES cat, no chance for SamyGO.
AFAIK only Games cat has some needed rights and capability to start custom programs

B550 has no game directory and some other plasmas too.
But you can use SamyGO Firmware Patcher to patch and use exeSDP.
Like Big and Colorfull subtitles, VideoARFix, NFS - SMB shares.. Video Player Enable for B550...
Buy you cannot use Game programs like browser...

So If you don't have Game menu, you can also have SamyGO Firmware on your TV.

Also you could check B550 exeDSP if there is CLauncher class existing. This class (to be specific CLauncher::t_Main) is in B650 FW responsible for launching the Games content. In fact, Games are loaded as shared library and Game_Main function is called, so this is the reason, why it has such "powerful" rights. CLauncher is not IMO used anywhere else, just for the Games content.

In theory - just an idea - it could be possible to patch B550 exeDSP to execute some thread during startup responsible for executing user "plugins" on request (i.e. by network)..

If exeDSP is compatible, we can do it with special button (via PVR code) or button combination...

Seems like the B550 series have no Content library feature support at all. I made some test with samples download of contents like animals and arts unpacked in usb key and i never see the choice item "content library media player" at the startup usb popup.