React error when using multi-column blocknote in nextjs 15 / react 19

[TheMythologist]

Describe the bug
Clicking on the slash menu will cause the following bug:

Error: Objects are not valid as a React child (found: object with keys {$$typeof, type, key, ref, props, _owner, _store}). If you meant to render a collection of children, use an array instead.

To Reproduce

• Use the example nextjs provided
• Add the multi-column plugin, with the guide provided
• Click on the slash menu
  Stackblitz reproduction

Misc

• Node version: 20
• Package manager: npm (i also got this error when I was using pnpm)
• Browser: any (specifically, I'm using Chromium-based browsers)

[TheMythologist]

Note: This bug is also triggered when strict mode is disabled in next.config.js

[sebasyii]

+1, facing this issue as well

[fedenuche]

I'm facing the same problem, but I'm not using NextJs; it's just a React project. My workaround was to downgrade the React version from 19.0.3 to 18.3.1