to add, the only time you have the option to hide the navigation bar is when you open a game, other than that, any sns apps from my knowledge, it stays, but if they dont give us the option, the least they could do is have it change to the same color as the app background or have it transparent to the color, the big block of white is super distracting, twitter screens have night mode itself, and to have a block of bright white forces one to turn down the screen light even more, why get rid of the "distracting" bezzels if you're not going to give us the freedom of the promised full screen use
There is something of a workaround.
In settings choose the gesture option, then choose the option to disable gesture hints so it isn't visible at all. You still have to use the swipes for all the buttons but you don't lose any screen real estate.
Also, to access the Google assistant swipe up the middle and hold it.
If you want to customise the look of the navigation bar, go to the Samsung store and install an app called Good Lock . This app has various add ons that you can install.
Once you have Good Lock installed, tap on Nav Star down the bottom of the list to install that add on.
You can also down load the Quick Star add on which gives you the option of moving the clock back over to the right hand side where we are used to it.
And all the add ons are free.
Hope this helps!
I've also had this frustrating problem. You can auto-hide the navigation bar by following the instructions on this webpage:
I have checked many other webpages, but this is the clearest one for those of us who do not know much about tweaking Android.
I hope it helps.