How to specify radio buttons in baseFieldDefinitions?
The radios/checkboxes are displayed based on the field's cardinality:


If the field can store more than one (e.g., unlimited: -&gt;setCardinality(-1), or 2,3,etc. -&gt;setCardinality(2), -&gt;setCardinality(3), etc.), it will be displayed as checkboxes.
If the field can store only one (i.e. -&gt;setCardinality(1)), it will be displayed as radio buttons.