What you are asking about has been available for years now and works very well. People just are not aware of it because this is a feature that has not been hyped for some reason.
We paid $175 for used Samsung S20+ phones about a year ago. They were released in 2020 and can be hooked up to a portable monitor through their USB ports and use a Bluetooth Keyboard and Mouse. They run the actual Microsoft Office Apps and many of the open-source replacements of course they are no slackers when it comes to editing images and video either.
The Android desktop that came with them is called Samsung DeX (short for Desktop Experience). I use them with AR Glasses or portable monitors. On the road phone itself is used as a touchpad and I use AR Glasses that cost $200 on sale at Amazon. Mine are RayNeo Air 2 AR Glasses. The later versions were on sale late last year.
We have splitters which allow the phone to be charged and use the monitors or AR glasses at the same time, but they go for quite a while using the phones built in 4500 mAh batteries without this. The newer versions of this phone cost more, but are more capable.
I have been a computer hobbyist for many years, so I have not given up my more typical laptops and desktops, using Windows and Linux operating systems, but for portability the phones with AR glasses come in very handy as laptop replacements that you can carry around in your pockets.
https://www.gechic.com/en/portable-touch-monitor-for-samsung-dex/
I don't use the touch monitor advertised... I just have one that I bought from Amazon which cost $100. It can be plugged into an A/C adapter but the phone's USBC port can power it as well.
The above picture is missing just the USBC cable that goes from the phone to the AR Glasses. But that is all you need to bring along to do normal computer tasks on the road .