To get the same effect in Ubuntu 18.04 as 16.04 I used the tweak tool to set a text scaling of 1.3. Additionally I had to set a scaling in Firefox's about:config in the layout.css.devPixelsPerPx property to the same 1.3 value. It's annoying that this has been removed from the normal UI as the underlying feature is still there and works fine.
To get the same effect in Ubuntu 18.04 as 16.04 I used the tweak tool to set a text scaling of 1.3. Additionally I had to set a scaling in Firefox's about:config in the layout. css.devPixelsPe rPx property to the same 1.3 value. It's annoying that this has been removed from the normal UI as the underlying feature is still there and works fine.