One time I found the player to be where the change happened so in the player I had to fish around for it's settings to stop fit, or upscaling. I see you already tried the TV settings.
How can I stop a Samsung K7000 from displaying a 4:3 DVD in “Fit to screen” mode?
I’m puzzled. One DVD containing a slide show in 4:3 displays in the correct format on my Samsung K7000. Another DVD, which displays in 4:3 on my wide angle MacBook changes to wide format on the TV and does not allow me to change it in Settings (4:3 Screen Size, This function isn’t available).
They are both DVDs, they are both 4:3, one works on Samsung K7000, the other doesn’t.
DVD player: Sony 4K UHD Upscale