I have just started back at this, basically starting over with the front-end coding. I want to begin putting what I learn to use as soon as possible, but I have a hard time thinking of things to create on my own. I am thinking that putting what I know to work doing whatever basic work might be required in a project might be useful. I don’t know, is this a little too ambitious? Should I just continue with the FCC curriculum until I can contribute to the nonprofit projects here? Thanks for your time/thoughts.
You can contribute to an OS anytime you want and feel comfortable in doing so.
That’s the whole definition of open source.
As a general rule of thumb, if you understand the source code means you can work with it 
That said some projects have lower skill ceiling to start contributing than others.
FCC tags some easy issues as first timers to help people start with it.
here you can find the one tagged as help wanted.
Clone the repo, look at the code and open issues and figure for yourself if you are able to contribute.
Honestly, you can start contributing with typo fixes. Someone’s gotta do it.