Download the font online, and extract the archive. You'll probably get a bunch of .tff files.
Move those files over to ~/.local/share/fonts/
# create dir if it's missing
mkdir -p "$HOME/.local/share/fonts"
mv *.tff "$HOME/.local/share/fonts"fc-match -a | grep -i 'DejaVu Sans'
> DejaVuSans.ttf: "DejaVu Sans" "Book"
> ...The name is the string in first parenthesis: DejaVu Sans
and its style is the string in second parenthesis: Book
Use these 2 strings to select the fonts in alacritty config.