I've received a hiring assignment and the interview NDA explicitly states that any idea/feature suggested during the interview process is the intellectual property of the company and they may implement them in their products. Is this a common practice? Feels straight-up unethical to me 😅

It seems unethical. They could basically give you a project that needs development and can use the ideas you mention and not hire you later.

You can ask them to pay for the time you are putting in for the completion of the project. Many companies pay for that. ex - stickermule.com

They are not even a small company. Pretty well known big name business in their domain. Funny, the NDA explicitly forbids candidates from sharing or using any information related to the platform but they can use candidate's ideas in their products 🥲

Just remember that larger companies have legal everywhere and it’s not representative of the engineering team. Personal experience - legal will force many of these, but the actual problems will be bog standard because we also don’t want to make someone work for a long time on a take home. If the problem itself looks reasonable and fun and is not asking you to build a whole project, just ignore the legalese