On the Lua side, you'll have to pass strings so your example works, as tables like those in setuphead({somehead}, {somesettings}) are actual Lua tables and follow Lua, not TeX, rules (see e.g. Lua reference in https://www.lua.org/manual/5.4/ or, better, CLD manual in http://www.pragma-ade.nl/general/manuals/cld-mkiv.pdf):

\starttext

\startluacode

--First example

for m = 1, 3 do

context.setuphead({'chapter'}, {before='hello'})

context.startchapter({title="I'm a chapter!"})

for i = 1, 3 do

context.input("knuth")

end

context.stopchapter()

end

--Second example

--We'll pass some strings to TeX

local nice = "ConTeXt is love, ConTeXt is life"

local somehead = 'chapter'

local sometext = 'vallejo-trilce-es'

context.setuphead({somehead}, {before=nice})

context.startchapter({title=somehead})

context.input(sometext)

context.stopchapter()

\stopluacode

\stoptext

I hope examples help.

Regards,

Jairo :)