Can I connect my XBOXONE to my HPall IN One Envy PC? It has an HDMI port, nervous to try w/o ...

You'll need to consult your HP computer documentation (manual, quick guide, etc) to determine whether that HDMI port on your desktop functions as an input or an output.

You can also just plug it in and see what happens. Worst case scenario, nothing happens.

There's nothing to fear. HDMI will not cause damage to another device if two output ports are connected with a cable. The engineers of HDMI knew this would happen sooner or later with the average user, because HDMI is often a symmetric,
male-to-male connection. Both HDMI devices first attempt a "handshake" with each other. If something is wrong (i.e. you've connected an output to another output), then both devices will refuse any further communication, and no more signal will be sent from
either port.

Problem @Merlin, most HDMI splitters are 1 out, 2 in. You need 2 out, 1 in. I have an HDMI running from the 2nd port of my TV, & another from the in port of my One. When I'm using the One, I plug that HDMI to my cable box, then switch it after I'm done so
the wife can watch w/o the One on.

can I plug my x box one s into my hp envy

Only if your setup has and HDMI in port and I believe video capture ability.

Now, if you have Windows 10 you can use the Xbox control app to stream your Xbox to your Envy then use the monitor to play (I do this if I want my big screen for other purposes.).

Try make sure your hdmi cable is connected in the right hdmi port,

I say this because my 4K HDR TV has 4 hdmi ports but only one of the hdmi ports supports 4K HDR the other 3 just do 4K SDR.

You can hook your Xbox One up to a PC if it has an HDMI input.

I dont have a HDMI port in my monitor.