I can use an expression to dynamically generate an alias based on a separate form selection, however when imported to Qfield this alias is not recognised and it shows the default alias instead. I need to generate dynamic alias labels for my form questions.

I don't know if this flows through to Qfield, but you can set this up in QGIS already by clicking 'Edit' on the Alias 'Data defined override' menu, then setting up your expression as desired