The reason you can't choose any skills to get expertise in is because you don't have any skills you're proficient in. Expertise requires proficiency in something first.
So to fix it - finish your character creation. Choose proficiencies from both your class and your background and then choose expertise.
A new Bard build. When selecting Expertise there are no skills to select from .
Character URL
https://ddb.ac/characters/47163540/1MDeJn
The reason you can't choose any skills to get expertise in is because you don't have any skills you're proficient in. Expertise requires proficiency in something first.
So to fix it - finish your character creation. Choose proficiencies from both your class and your background and then choose expertise.
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