On 08 Jun 2021, Marilyn Manson wrote
in alt.home.repair:

I have a Samsung Smart TV (UN50NU6950FXZA) which just started
acting up. When powering on it no longer defaults to the HDMI
input coming from the cable DVR box. The TV now defaults to the
Samsung TV Plus app*, which a set of free TV channels provided by
Samsung. I have to manually switch the source to HDMI if I turn
the TV on.

*Well, it sort of defaults to the TV plus app. It shows the TV
Plus logo in the upper corner and it displays the name/number of
the channel that it was last tuned to, but it doesn't actually
display the channel. The screen just goes blank after a couple of
seconds. If I select a different channel, it will then display it.
When it first powers on it's kind of in a TV Plus-esque limbo.

I called Samsung and they tried to blame my cable provider's
equipment. When I told them that I tried both a different HDMI
cable and even a different cable set-top box, they were stuck. The
only other suggestion they had was to try a factory reset. Great,
now I'll have to reload all my apps, hoping I remember what
password I used years ago, etc.

I'm really just venting but also sort of hoping that someone has
other suggestions to try before I do the factory reset. No, there
is no "Default Power On Source" that needs to be selected in the
settings. If there is a signal at the HDMI port, it's supposed to
default to that.

My Samsung TV remembers its most recent input and will return to it
when you turn it on. This seems like the most logical way for it to
work.

The TV has a screen where you can set it to automatically install
software updates, or to check manually for updates. Maybe there's a new
update that will fix a known problem.

I wouldn't hesitate much to do the factory reset. I only have a couple
of apps that require passwords and I know them.