Just updated firefox to the latest release. They have removed the lines between tabs and makes it horrendous to do use (In my opinion).
There is no option to fix this in the UI. However you can fix it at least for now in about:config.
Be careful doing this, I accept no responsibility if you break your browser.
Type about:config in your address bar no https:// or anything else. Hit enter.
Then copy and paste this into the search box.
browser.proton.enabled
Click the icon to the far right to toggle it to
browser.proton.enabled = false
Borders should appear straight away.
You can toggle it back or click the reset button to reset this.
There is no option to fix this in the UI. However you can fix it at least for now in about:config.
Be careful doing this, I accept no responsibility if you break your browser.
Type about:config in your address bar no https:// or anything else. Hit enter.
Then copy and paste this into the search box.
browser.proton.enabled
Click the icon to the far right to toggle it to
browser.proton.enabled = false
Borders should appear straight away.
You can toggle it back or click the reset button to reset this.