Is there a way to use my iPhone photos as a screensaver on my Samsung TV

If you have the Apple TV box, then you can set a screen saver from photos through iCloud or Home Sharing (from computer).

If you have a smart TV with the Apple TV app, then you can’t use that for screen savers directly.

My old big screen TV set is getting some serious screen burn and does not have Smart capabilities, so I am considering the purchase of a Samsung Smart TV. As of 2018 that the manufacturer has included Airplay and/or the Apple TV app in their OS (TIZEN). I would imagine this holds true for Samsung Smart TVs manufactured in 2021. That being said, I would hope that the functionality of the Apple TV app includes the ability to access Shared Albums in Photos. We'll see.

If it's any help I was able to find the following information online.

Samsung TVs with Airplay and/or Apple TV app

The following Samsung Smart TVs feature the Apple TV app and work with AirPlay 2:

• Samsung QLED 8K Q9, Q8 Series (2019, 2020): 
• Samsung QLED 4K Q9, Q8, Q7, Qx Series (2018, 2019, 2020): 
• Samsung UHD 8, 7, 6 Series (2018, 2019, 2020):
• Samsung FHD / HD 5.4 Series (2018, 2019, 2020):
• Samsung Serif Series (2019, 2020):
• Samsung The Frame Series (2018, 2019, 2020): 
• Samsung The Sero Series (2019, 2020): 

And these Samsung TVs offer AirPlay 2:

• Samsung FHD / HD 4, 5 Series (2018): 
• Samsung UHD 6, 7, 8 Series (2018, 2019): 
• Samsung QLED 4K Q6, Q7, Q8, Q9 Series (2018, 2019): 
• Samsung QLED 8K Q9 Series (2019): 
• Samsung The Frame Series (2018, 2019): 
• Samsung Serif Series (2019): 

You could use AirPlay but IMHO that would be a foolish. I would recommend that you ask Samsung about changing it screen savers and also please try to be more specific, what I mean is in my home we use Apple TV (and use it's screen savers) and we also toggle to DirecTV and use it's screen savers. Your environment may be different so you need to let them know in which environment you want to change the screen saver.

That would be down to your Samsung TV.

Check its user guide or contact Samsung support and see if you can send over some pics to it for user as a screen saver.

No, the Apple TV app has no way to access shared photos. Its only there for access to the iTunes store content, and Apple TV+ subscription service content. Nothing else.