These, perhaps, are the farthest seen emissions of heavier elements, but I don't consider these emissions to be from large redshifts.
Their conclusion states:
"We have reported the first results from the CECILIA program (JWST PID 2593), which obtained ultra-deep ∼30 hr NIRSpec/G235M observations of 33 star-forming galaxies at z ∼ 1–3.
...
We significantly detect emission lines of eight different elements (H, He, N, O, Si, S, Ar, and Ni)..."
With the JWST, we are seeing objects as far out as z = 13, IIRC.
As Rob notes, even at z = 3, it was 2,172 million years of age. Given enough telescopic power, if stars formed at the earliest moments some models predict, and if they go SN, with their predicted very short life-span then we should be able, in principle, to see spectra from much greater redshifts...someday. Or am I missing something?