Biblatex missing characters in Libertinus

[Wolfgang Engelmann]

Running a biblatex document for the pdf output I get errors for missing 
characters.
What is the best way to remove these errors?
Wolfgang


Missing character: There is no ▴ (U+25B4) in font 
[LibertinusMath-Regular.otf]
Missing character: There is no œ (U+009C) in font 
[LibertinusSerif-Regular.otf]

Missing character: There is no 𝜇 (U+1D707) in font 
[LibertinusSerif-Regular.o
Missing character: There is no 𝜑 (U+1D711) in font 
[LibertinusSerif-Regular.o