GeForce Now is a great way to play games on a handheld gaming PC, such as a Steam deck. You can play games that are not available on its Linux-powered handheld. For example, Destiny2. You can also save a pile of battery by streaming instead of playing it normally locally. What's not so great about it is that you're trying to install GeForce Now as something similar to an easy-to-use app. It has traditionally needed a good deal of tweaking, and I've long wanted the GeForce Now app on the steam deck. Thankfully, Nvidia is now bearing the brunt of fiddling with the settings for you.

New GeForce Now installation files are now available on Steam Deck, ROG Ally, Legion Go, and MSI Claw. It includes a script that effectively installs Google Chrome, the web browser of your choice to run GeForce Now, and tweaks the launch options to optimize for each handheld.

You may wonder why you need to install a browser-based game streaming service, but at least on Steam decks, you can't use many of the Steam deck's controller configurations through Google Chrome (so while you're playing the game on GeForce Now). You cannot adjust the browser settings further. 

There's already a dedicated GeForce Now app for windows, so I don't know exactly what it's doing with the mentioned Windows-based handheld.

I gave go to my Steam deck to download the script and see exactly how it works.

This script sets Nvidia GeForce Now on your Steam deck.

And at the end of the process, lo and behold, I added a new GeForce Now shortcut to my Steam library This new script makes the process quick work and is much easier for beginners.

In order for GeForce to work as intended within the newly created shortcut, it was necessary to tweak the Steam gamepad settings, but setting the controller configuration of the Steam deck in Geforce Now to "Gamepad with Joystick Trackpad" could work well. There is a tendency. If necessary, you can always press the Steam button to tweak the controller settings for each game.

I still want an officially licensed application made by Nvidia for Steam, which seems to have been in discussion at some point in time, though for now I would take an effort to simplify this process for all.