I installed that font to be sure (on Windows). There are 2 lines of text, but it looks like MC suppresses the ellipsis when there's html formatting on the expression (or some other rule, I'm not sure)
I think the problem could be the mode 2 on the fixspacing()... I think there's no mode 2? When I use mode 2, I get the ellipsis regardless of which font I use. When I use mode 1, it works without ellipsis with both fonts.
This simplified expression also works with both fonts for me (also adding "size" if needed):
<font face="Ubuntu Condensed">[Name]if(isempty([AMG Composer]),,<font color="2184C6">
[AMG Composer])
or
<font face="Ubuntu Condensed">fixspacing([Name]if(isempty([AMG Composer]),,<font color="2184C6">
[AMG Composer]),1)
Edit: Note that a single whitespace at the end of the first line will cause the ellipsis to show up. The whitespace rules in expressions are a bit weird - whitespace is ignored right after a comma in an expression but not after an html tag, so if there's a space there MC will consider it as text and add the ellipsis to indicate there's something there.