The ubuntu flavor and look+feel has been added to the stock gnome3 – which is not much but I dislike the fat font and the unity-style dock.. also there is something about that purple.

anyway, easy fix: get these packages (in order of how much you want to be gnome-ified)
1) apt install gnome-session
2) update-alternatives –config gdm3.css (select gnome-shell.css)
3) apt install ubuntu-gnome-default-settings
4) apt install vanilla-gnome-default-settings vanilla-gnome-desktop

key differences are:

• No Ubuntu Dock
• No app indicator support
• Adwaita GTK and icon theme
• Cantarell font is used
• Default Shell theme
• App windows only show a ‘close’ button
• Symbolic icons used in App Menu
• Activities Hot Corner

sources:
https://itsfoss.com/vanilla-gnome-ubuntu/
https://technastic.com/install-stock-gnome-shell-on-ubuntu/