I'm afraid it's impossible to switch to classic mode now. Previously I could see /Use Unified Interface only/ in Behavior in Settings, now I can't see it either. I couldn't find this /Use Unified Interface only/ description in the corresponding official documentation either. The official documentation also no longer describes how to switch to the classic interface.
Now, the design of product interfaces is moving towards the new UI, I recommend you try the new UI, which also has great advantages and is actually easier to use, and the new UI will be updated according to the user's needs. UI/UX design for Dynamics 365 - Dynamics 365 | Microsoft Learn
If my answer was helpful, please click Like, and if it solved your problem, please mark it as verified to help other community members find more. If you have further questions, please feel free to contact me.
Best regards, Cui Hao
Under review
Thank you for your reply! To ensure a great experience for everyone, your content is awaiting approval by our Community Managers. Please check back later.