Frontendmentor provides designs, and challenges can be completed in any stack. The challenges can also be as simple or complicated as you like.
2. Chingu.io
Chingu puts participants into groups for a 6-week team project, which provides team work experience.
3. Freecodecamp Projects
While freecodecamp lessons are not great the exercises are amazing.
4. Exercism
Exercism is a good place to develop programming language fluency. It supports 62 different programming lanauges. It is free and mentoring is available if needed. I find most of the mentors very knowledgable. I have also mentored on exercism and it was a great experience.
