The DejaVu fonts are a superfamily of fonts designed for broad coverage of the Unicode Universal Character Set. The fonts are derived from Bitstream Vera (sans-serif) and Bitstream Charter (serif), two fonts released by Bitstream under a free license that allowed derivative works based upon them; the Vera and Charter families were limited mainly to the characters in the Basic Latin and Latin-1 Supplement portions of Unicode, roughly equivalent to ISO/IEC 8859-15, and Bitstream’s licensing terms allowed the fonts to be expanded upon without explicit authorization.
The full project incorporates the Bitstream Vera license, an extended MIT License, which restricts naming of modified distributions and prohibits individual sale of the typefaces, although they may be embedded within a larger commercial software package (terms also found in the later Open Font License); to the extent that the DejaVu fonts’ changes can be separated from the original Bitstream Vera and Charter fonts, these changes have been deeded to the public domain.[1]
I use “mono-9” in all my terminals, including for emacs. On my Debian trixie system, that maps to DejaVu Sans Mono in the fonts-dejavu-mono package.
https://en.wikipedia.org/wiki/DejaVu_fonts