Check my attached video.
Thank you.
When using Korean characters with English characters in a cell, Korean characters become question marks
Answers approved by DevExpress Support
We have fixed the issue described in this ticket and will include the fix in our next maintenance update. To apply this solution before the official update, request a hotfix by clicking the corresponding link for product versions you require.
Note: Hotfixes may be unavailable for beta versions and updates that are about to be released.
In this case, the same problem occurs.
I replicated this problem - see the T849461: Mixing different Korean fonts in a cell that Korean fonts are set, each font is not applied thread. I will forward this ticket to our developers to research.