Update Madagascar and try “\F19”.  The fonts can be found in https://github.com/skishore/makemeahanzi

The following example is from rsf/rsf/sfgraph:

str1 = "你好马达加斯加"
Result("chfont",None,
       '''
       spike n1=1000 k1=300 | 
       bandpass fhi=2 phase=y |
       wiggle titlesz=5 wheretitle=b wherexlabel=t
       title=" \F19 %s" crowd2=0.5 label1="\F19 %s \F1"
       label2="\F19 %s \F1 " max2=1. min2=-.5 labelsz=5
       '''%(ch2uni(str1),ch2uni("时间"),ch2uni("振幅")),stdin=0)