Metallicity estimates and ranges for z ≥ 1 DSFGs from Nagao et al. (2012, N12), De Breuck et al. (2014, dB14), Wardlow et al. (2017, W17), Rigopoulou et al. (2018, R18), De Breuck et al. (2019, dB19), and ULIRGs from Pereira-Santaella et al. (2017, P17). For SDP.81, we show our best-fit solution Z = 0.5 Z_⊙ (circle); we also include a tentative uncertainty of ±0.25 Z_⊙. The sub-solar metallicity in SDP.81 is consistent with the upper limit of ≤2 Z_⊙ from Rigopoulou et al. (2018), and comparable to the lower range of metallicity estimates in other high-z DSFGs.