Websites for software knowledge:
https://www.linkedin.com/online-training
https://helpx.adobe.com/uk/support/creative-cloud.html
Websites for design specific knowledge:
https://developer.apple.com/design/ - inc guidelines
https://developer.android.com/about - inc guides (*tech heavy)
https://www.ustwo.com/blog/design/ - articles/handbooks inc: Pixel Perfect Precision
Websites for design inspiration, practice and discussion:
http://www.digitalartsonline.co.uk
https://www.itsnicethat.com/categories/digital
https://www.itsnicethat.com/double-click
http://www.creativereview.co.uk/cr-blog
http://www.designobserver.com/
http://www.eyemagazine.com/blog
https://www.creativebloq.com/