XMind

https://www.xmind.net/faq/question/trial-and-full-version-xmind-2020/

There is no free version, but evaluation version.

Before purchase, you’re using a trial version.
It's for evaluation purposes only. Some features are inactive. And all exported images and PDFs would come with watermarks.

With a evaluation version, the functinalities are limited. Exported pnd and pdf contains watermark. Markdown export is not available with the evalution version probably because it's impossible to watermark a markdown file.

XMind does provide much more styles for the mind map diagrams than that of 幕布mubu, you can simply screenshot it to avoid watermark. One drawback is that you can't remove image background color. XMind's image export support no-background mode but there is watermark. That's the tradeoff.

Instead of syncing your notes, XMind saves your notes as files in file system.

All in all, the proper way to use this app without purchasing is to create mind maps with this tool and take a screenshot when you need to.