r.spread(1grass) on Linux
The text d1cf4f168567, as Debian 12 (Bookworm) shipped it.
Simulates elliptically anisotropic spread. Generates a raster map of the cumulative time of spread, given raster maps containing the rates of spread (ROS), the ROS directions and the spread origins. It optionally produces raster maps to contain backlink UTM coordinates for tracing spread paths. Usable for fire spread simulations.