SampleDbContext.cs

public class SampleDbContext : DbContext
{
    public SampleDbContext(DbContextOptions options)
        : base(options)
    { }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);

        foreach(var entity in builder.Model.GetEntityTypes())
        {
            // Replace table names
            entity.Relational().TableName = entity.Relational().TableName.ToSnakeCase();

            // Replace column names            
            foreach(var property in entity.GetProperties())
            {
                property.Relational().ColumnName = property.Relational().ColumnName.ToSnakeCase();
            }

            foreach(var key in entity.GetKeys())
            {
                key.Relational().Name = key.Relational().Name.ToSnakeCase();
            }

            foreach(var key in entity.GetForeignKeys())
            {
                key.Relational().Name = key.Relational().Name.ToSnakeCase();
            }

            foreach(var index in entity.GetIndexes())
            {
                index.Relational().Name = index.Relational().Name.ToSnakeCase();
            }
        }
    }
}