Cyberpunk 2077 is a massive and dense open-world RPG that's completely full of things to do. Thanks to the cloud-based streaming functionality of google Stadia. This means you can explore Night City anywhere in the world you have access to a Wi-Fi connection or a mobile data signal.
Google Stadia is the best place to play Cyberpunk 2077 and this also means you can technically play Cyberpunk 2077 with touchscreen controls. Even though it can be played this way I'd be surprised if anyone could actually complete the game even on the easiest difficulty. I have played for a couple of hours of my time on my Google pixel 4 XL and well how to put this in kind words these were two hours of my life I'll never get back.
Probably I am one of the few people in the world using touchscreen controls with some Stadia games. I use them to jump into Elder Scrolls Online every day for a few minutes so I can claim my daily reward. I just open the game, navigate the menus with the touch buttons, and take care of things in a matter of seconds.
In fact, some games are remarkably playable with touchscreen controls. Turn-based games such as Baldur's Gate 3, Into the Breach, and Valkyria Chronicles 4 don't require speed reactions or concentration so these games we can play as if they were mobile natively. You are not going to find many options like a mouse cursor that clicks they can be found in other mobile games, you can do it only with your fingers.
But, playing real-time games, gets more complicated. Simultaneous button inputs aren't reliable reliably so you might need to tap multiple times. Without the tactile feeling of where a button is located is a matter of getting where the spot to touch might be. Also, part of the layout covers areas of the screen, so you will not be able to see all of the game while playing either.
The biggest issue of all, especially for single=person shooter games such as Destiny 2 and Cyberpunk 2077, is that the triggers are also on the phone screen instead of on the back, like a controller. This means we need to be very agile with our fingers creating an almost impossible grip to be able to use the analog sticks and fire a gun at the same time. It doesn't work well. The ultimate result is usually stopping to shoot and never moving while attacking at the same time. If you've ever played a shooter, you'll understand why this might be a bummer
Google Stadia, can improve this situation a little bit, but I'm not sure enough people will actually want to play Stadia games this way. For starters, only to remap where the virtual buttons are supposed to be located would be a great starting point, or adjusting the size, color, and opacity of the button outlines. I'd also love some macro settings of some kind.
Most games that rely entirely on virtual buttons play extremely well because the entire control scheme is built around that game. Call of Duty Mobile is a good example of that, is smooth, responsive, and fun despite being a mobile game with touchscreen controls.
For all the reasons stated above, I could see this still being somewhere useful even in Cyberpunk 2077 as-is. Try Stadia, go into Cyberpunk 2077 and turn in some quests, do some inventory management, or even talk to your fellow gamers and progress a few storylines.
The roadblock is as soon as you're asked to do anything that requires combat or careful driving. For that reason, you're better off just plugging in a controller or waiting until you can play on Chromecast or browser instead.