If you are interested than I got some good news for you. The http://linuxupskillchallenge.com Linux command-line / sysadmin "challenge" course will start on Monday.
It is a fully free and open-source course (it costs nothing but your time) where you can start learning about Linux or deepen your knowledge.
Daily lessons will appear in the subreddit called r/linuxupskillchallenge from this coming Monday - which will also be used for support/discussion. Furthermore, it is a "rolling" course, which restarts every month.
As I have mentioned above, the course is free, but it does require some commitment - but if gaining/growing these skills is important to you, then you now have no excuse.
I hope you will have fun while doing the challenge 🔥 🔥