Related to this xelatex question.
I get Missing character: There is no π in font cmr10!. So I set the unicode font to cmu (computer modern unicode) as advised by this question for xelatex
\font\cmu=cmu10 at 10pt
\cmu π
and try again but nothing changed, it still complains Missing character: There is no π in font cmu10!.
I also tried the ecrm1000 font as advised by this answer regarding xetex.
The solution of downloading a different(?) computer modern unicode font is not acceptable because it requires installing the fonts into an OS font directory with root permissions, and I will only use default fonts, or fonts that can be included along side the source tex file.
CMU Serifwas just a latex equivalent reference tocmu10. – user8578151 May 15 '18 at 11:00