You need HDMI 2.1 for eARC. The 2020 TCL offerings with the mini led will support it. Not released yet. The following is from Digital Trends :
The Audio Return Channel (ARC) is an HDMI 2.0b feature that lets audio move back and forth over an HDMI cable between a TV and an A/V receiver or soundbar. Unfortunately, the limited bandwidth of HDMI 2.0b means that audio is often compressed and reduced down to stereo. With Enhanced Audio Return Channel (eARC), we can now get uncompressed, full-resolution audio over HDMI 2.1 connections. Dolby Atmos is a perfect example. With ARC, Atmos only works when using Dolby Digital Plus, a compressed audio signal. eARC lets Dolby Atmos give its best performance using Dolby TrueHD, a lossless, high-resolution audio signal.
This will simplify system setups dramatically because it means users can connect everything to their TV and then run a single HDMI cable to their receiver or soundbar without losing sound quality. Fewer cables, less mess, better sound!