Since the Challenge difficulty has been reworked, if you were already playing on it, switch your difficulty to "Hard" - it’s the same difficulty but without save restrictions. On Challenge, the manual save button will no longer be available everywhere - only in taverns. When you try to change the difficulty, the game will warn you that you won’t get the achievement. Ignore this and switch anyway, since you were already mid-playthrough, you wouldn’t get the achievement for this difficulty regardless. Essentially, you were playing on Hard, as Challenge didn’t differ before - I was keeping it as a placeholder, so nothing really changes for you.

In general, regarding Challenge - you can save in taverns, and you can also craft a Save Ration, which allows you to save anywhere. If you try to load a Challenge save on a different difficulty, you won’t receive the achievement. (Not recommended for a first playthrough)

I’ll be honest - I haven’t fully tested this mode, as it would take a lot of time, so play at your own risk for now. I’ve added a tag to grant the achievement later if someone completes it before achievements are officially added. Hopefully it works 🙂 In any case, the most important thing is not to lose your save after finishing the game. Once achievements are added, you’ll need to load that save and the achievement should be granted.

But remember - if you were already on Challenge before patch 0.9.5.6, make sure to switch to Hard.