This issue is caused by List v3 only, not reproducible in List v2.
Steps to Reproduce
Pre-req: Enable List v3 plugin
1) Go to the sys_user table
2) Add the "Language" column
3) Edit the Language and click on dropdown
Expected - You should see the value of what the default choice is for the instance
Actual - The system is displaying the code verbatim.
Currently, there is no workaround. To receive notifications if and when more information is available, subscribe to this Known Error article by clicking the Subscribe button at the top right of the article.
Related Problem: PRB1182072