After 30 years, it looks like a.out support will finally be removed from Linux. While the once-popular file format (which was replaced by ELF in the mid-1990s) was deprecated in 2019, a patch has been proposed (https://bit.ly/lxf286patch) to remove a.out support completely from the kernel.
The proposal by Borislav Petkov appears to have broad support from other upstream developers, and while it may not make the 5.17 merge window, we could see it disappearing later this year.