I am running in-home streaming on a headless PC to my laptop, and in many games I was having an issue where my cursor was invisible, making it nearly impossible to play. A Valve employee confirmed here:
https://gtm.steamproxy.vip/groups/homestream/discussions/1/540738052135928090/
that it is an issue with Windows 10 hiding the mouse cursor when no mouse is plugged into the machine. Every topic I found always ended with the OP saying they fixed it simply by plugging a mouse into the host PC.

For me, however, I do not have a spare mouse handy, and it seems asinine to have a mouse dedicated to being a "dummy" just to be able to play games. So I started trying stuff out on my own, and I am very glad to have found a solution!

1) Search "mouse key" in the Start menu and click the result reading "Change mouse key settings"

2) Under the "Mouse Keys" section, turn on "Use numeric keypad to move mouse around the screen"

3) Launch the on-screen keyboard that comes with Windows, click the "Options" key in the lower left, and check "Turn on numeric keypad." Turn on NumLock.

4) The on-screen keyboard doesn't need to stay open while the game is running, so you can close it. You should now be able to use your mouse while streaming from a headless PC.

I hope this helps someone; I sure wish someone had figured this out before.