It depends on how you do it.
Medium as an import feature, which copy-paste your article and creates proper canonical link: https://help.medium.com/hc/en-us...
This will not penalize your SEO.
Copy-pasting content to Quora might penalize your SEO. Moreover, it isn't a good practice: Quora answer should be shorter than a blog post. If you want to save time with content distribution on Quora, you can use QApop content draft: https://youtu.be/VtlN76vHj_4
Should not be penalized. But you can also use any GPT3 software to rewrite parts and be on the safe side.
From my experience, having platform focus and expanding as you grow in B2B SaaS is the best strategy.
Because if you spread yourself too thin, you won't dominate any platform, and you will likely be considered a spammer on most.
What do you think?