The keyboard shortcut to select address bar (in chrome) is
Ctrl + L,
ALT D, or
F6. But what is the keyboard shortcut to un-select the url and get back to the webpage? If I hit
tab, the focus cycles within suggested urls.
F6 will focus onto the omnibox, and additional F6 inputs will cycle through various control sets, eventually coming back around to the webpage (it will return focus to whatever control you left off from).
Also note that you can use Shift+F6 to cycle in reverse, and so, i.e., you can focus to omnibox F6 and then return focus to webpage Shift+F6.
The above is confirmed working as of Google Chrome is up to date Version 83.0.4103.61 (Official Build) beta (64-bit)