\(Q=\dfrac{a}{b+mc}+\dfrac{b}{c+ma}+\dfrac{c}{a+mb}\)
\(=\dfrac{a^2}{ab+mac}+\dfrac{b^2}{bc+mab}+\dfrac{c^2}{ac+mbc}\)
\(\ge\dfrac{\left(a+b+c\right)^2}{\left(m+1\right)\left(ab+bc+ca\right)}\ge\dfrac{3\left(ab+bc+ca\right)}{\left(m+1\right)\left(ab+bc+ca\right)}\)
\(=\dfrac{3}{m+1}\)