If you are looking for specific firmware files, checking the TCL Support Page for your region is the best way to get the latest authorized version.
TCL 50EP660 is part of the RT51 platform (often using the V8-R851T02-LF1Vxxx firmware chassis) and runs on Android TV firmware tcl 50ep660 upd
Complete Guide to TCL 50EP660 Firmware Update (UPD & IMG Methods) If you are looking for specific firmware files,
is directly through a live internet connection. This method retains all user data, signed-in applications, and custom image calibrations. firmware tcl 50ep660 upd
Go to Settings > Device Preferences > About > System update > Local update .