what's the most common standard serif font on linuxes? ⁖ Times New Roman on Windows and Mac.
Another good one in most linuxes is DejaVu family. See: Best Unicode Fonts for Programing.
what's the standard Chinese font on most linuxes?
The WenQuanYi (文泉驛) family. This family does not include brush-style (Kei) typeface though. 〔☛ Chinese Character Etymology and Script Styles〕 This is the only Chinese font installed with Ubuntu by default.