Many streamers have voice search capabilities built into their remote controllers and can be used with just about any app.
Netflix is finicky with web browsers. Use Google Chrome for Netflix and 4K Dolby Vision and Dolby Atmos will not be supported for output.
Using a browser on Windows for Netflix requires using Windows 10 or 11, Microsoft edge browser, the Microsoft Dolby Access app for Windows, sound output set to “Dolby Atmos For Home Theater” and Netflix highest tier service for 4K UHD support.
My Mac mini M1 is connect to my receiver. I use it daily to web browse and listen to music. But, come movie streaming time, I fire up the Apple TV 4K. The Amazon Fire Cube Gen 3, NVIDIA SHIELD TV PRO, Roku Ultra 4800X, XBOX Series S and LG C1 TV do not get used for streaming nearly as much as the Apple TV 4K. Having them all connected to the system all at once using HDMI-CEC is a f#%king nightmare and that is no longer done.
Regarding the system in question, I can’t remember if the 6013 supported eARC out of the box. No matter with the Roku and Atmos/DD+ bitstreams. It should be fine still connected to the TV.
The most compelling reason to leave the Roku Ultra 4800X connected directly to the TV is HDR10+ capability. The Roku should detect it in the Samsung TV automatically and output everything in HDR10+ by default. The Marantz SR6013 does not support HDR10+. Dolby Vision would be output by default by the Roku when connected to an AVP/AVR and/or TV that support it.
Samsung TVs had great Universal Remote functions even for devices connected to a receiver. If that is still the case, the TV Remote Controller may be able to control the Roku after setup.
I’m confident the recommended audio settings for the Roku Ultra 4800X will work here using a connection to the TV or to the receiver. They worked for me using each of those connections.