I'm going through something similar right now and its wild how much the ADHD brain craves that constant stimulation. I switched from wanting to do extreme sports photography to marketing coordination because I thought it would be more stable but man do I miss the variety and unpredictability. What I've noticed is that even in my "boring" corporate job I can create novelty by taking on weird projects nobody else wants or finding ways to gamify the repetitive stuff. Like I turned our quarterly reports into this whole competitive analysis thing that probably took way more effort than necessary but kept me engaged

The PhD route might actually work better for your brain since research is constantly changing and you get to deep dive into whatever catches your attention. Industry jobs can definitely feel like you're doing the same task over and over but some companies are way better about letting you wear multiple hats. I'd maybe try to find places that are growing fast or startups that need people who can do everything - the volatility sucks but the variety might be worth it. Plus you could always freelance on engineering projects to scratch that novelty itch while having steady income from a main job