The first period-41 oscillator in Conway's Game of Life was just found by Nico Brown: https://conwaylife.com/forums/viewtopic.php?p=163972#p163972

With that, oscillators of every period are known: Conway's Game of Life is omniperiodic! This has been one of the major open problems in the study of Conway's Game of Life even since its invention over fifty years ago.

This comes just 7 days after the second-to-last period, period 19, was discovered.