Disable Overlay Scrollbars
You may dislike the lack of buttons at the top and bottom of your scrollbar, as well as the thinness and occasional inconsistency of them.
Disable them by changing the ubuntu-overlay-scrollbars setting in org > gnome > desktop > interface to false. You can do this with dconf-editor or by running a gsettings command in the terminal.
Alternatively, you can enable them again (the fallback is not so hot) by changing the setting to true.