TITLE: GCN CIRCULAR NUMBER: 29304 SUBJECT: GRB 210104A: JCMT SCUBA-2 sub-mm observations DATE: 21/01/15 21:55:33 GMT FROM: Ian Smith at Rice U I.A. Smith (Rice U.), D.A. Perley (LJMU), and N.R. Tanvir (U. of Leicester) report: We observed the Swift UVOT location of GRB 210104A (Troja et al., GCN Circ. 29233) using the SCUBA-2 sub-millimeter continuum camera on the James Clerk Maxwell Telescope. The observation started at 08:23 UT on 2021-01-05, with the mid-point of the run at 0.894 days after the burst trigger. Exposures totaling 1.0 hours were made in very good weather conditions. No source was detected, with the RMS background noise being 1.7 mJy/beam at 850 microns and 14.5 mJy/beam at 450 microns. We thank Kevin Silva, Mark Rawlings, and the JCMT staff for the prompt support of these observations that were taken under project M20BP026.