Certification Courses and Practice Exams (Cloud/DevOps)

1. Adrian Cantrill - https://learn.cantrill.io/
2. Stephane Maarek - https://courses.datacumulus.com/#aws-certifications
3. Tutorials Dojo - https://tutorialsdojo.com/
4. cloudskills.io - https://cloudskills.io/

Certification Courses and Practice Exams (Linux)

1. Linux Academy - https://linuxacademy.com/
2. Linux Foundation - https://www.linuxfoundation.org/
3. Sander Van Vugt - https://www.sandervanvugt.com/

Security

1. https://www.hackthebox.eu/