Thank you for the valuable feedback. I'll try to improve that more in future posts and add more paragraphs here.
I don't think whoop influenced my rhythm that much. But I had quite a steady rhythm already, so it wasn't too much of a problem. I think I mostly profited from whoop by having an assessment for my quality of sleep. This made it much easier for me to decide how to prioritize my work, e.g. when I should do intellectually intense stuff and when light work. I haven't tried any of your other suggestions, e.g. CBT, so I cannot comment on them. But thank you for sharing your experiences.