Quick take
Use LG LT1000P or a verified LT1000P-compatible cartridge. LG also sells LT1000P multi-packs, useful as an OEM cost benchmark.
Correct replacement filter
LG’s LRFS28XBS product page identifies LT1000P as the related water-filter accessory, and LG Canada lists Water Filter Model Name LT1000P.
OEM vs compatible
OEM gives the simplest match; compatible cartridges compete mainly on recurring cost.
What to compare
Fit, certification, cartridge capacity and annual cost matter more than headline contaminant counts.
Replacement planning
LG recommends periodic replacement for LT1000P-family cartridges; use the refrigerator indicator and current instructions.