I've not saved any of mine via the new Save/Load function and have still had autosaves when the game's occasionally crashed, so it is working.
It's currently set to a high number of turns by default, however, and that setting can't be globally changed and saved, only per character. That could use a fix.

The autosave is a separate file, you have to manually rename it for ADOM to pick it up. Or has this changed?

Then there should be a notice about where that file is located and that the autosave file have to be renamed. But for many users that would be too much to search a file and rename it. Any autosave file should be visible at the character load screen.

It works for me, didn't need to rename anything.

Autosaving works, but you need to rename the file when you want to load an autosave. The difficulty is to find the autosaved file.

Fixed.