I often use Greek letters in my LaTeX documents. To avoid unreadable source files with \alpha, \phi, etc., I use Unicode and Greek letters directly. This is easy to configure with commands like
\DeclareUnicodeCharacter{03B1}{\alpha}
For typing, I switch between english and Greek keyboard layouts.
Both LaTeX and Unicode recognizes variants for a few Greek letters
U+03C6 φ GREEK SMALL LETTER PHI:
\varphiin LaTeXU+03D5 ϕ GREEK PHI SYMBOL:
\phiin LaTeXU+03B5 ε GREEK SMALL LETTER EPSILON:
\varepsilonin LaTeXU+03F5 ϵ GREEK LUNATE EPSILON SYMBOL:
\epsilonin LaTeX
Although, my Greek layout does not proposes multiple variants for these letters.
Does someone know an appropriate way to input a specific variant of these Greek letters?