Using open source as a springboard is also a great way. As you mentioned, much harder... but still worth it in the long run.
I can't speak to the banning for no reason on Upwork, but I think that's risk for any platform. I know many people who were banned from Facebook and Twitter for no reason. Much harder to rebuild a following than land a few initial projects IMO.
With that said, you can always use Upwork as a springboard. Some of my best clients started on Upwork and moved to direct work due to the relationship we built.
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