OKL4 is the most widely used L4 spinoff, and Kernkonzept's L4Re based on Dresden's Fiasco comes much closer than seL4. https://l4re.org/ https://l4re.org/ I do

OKL4 is the most widely used L4 spinoff, and Kernkonzept's L4Re based on Dresden's Fiasco comes much closer than seL4. https://l4re.org/ https://l4re.org/ I don't consider seL4 current, more like academic research.