When you select by long-pressing, the selection includes light blue "handles" under each end that can be dragged to enlarge the selection. Also at least in a text area the menu does include "Select All". Other than that... if you have a keyboard that includes a Ctrl key you might try Ctrl-A, but on-screen keyboards probably don't have one.
@leocg Nope! It is turned on, and no site opens in a corresponding installed app. I'm sure I'm doing something wrong, but no clue. I don't even see any option to switch to when I'm in a site that has its app installed.
I'm using a xiaomi redmi note 9s. Android 10, miui 11. Something hidden maybe.
@frack Regarding your second question, it seems to already has the answer on itself.
Your bookmarks stored in Sync servers are encrypted but not your bookmarks themselves.