I鈥檝e found a solution for this, which involves setting a custom naming function - Duplicate identifier on Typescript type generation due to _ prefix 路 Issue #6925 路 dotansimha/graphql-code-generator 路 GitHub
Using this, I can get the generator to produce the following types output:
export enum CategoryModelOrderBy {
_CreatedAtAsc = '_createdAt_ASC',
_CreatedAtDesc = '_createdAt_DESC',
_FirstPublishedAtAsc = '_firstPublishedAt_ASC',
_FirstPublishedAtDesc = '_firstPublishedAt_DESC',
_IsValidAsc = '_isValid_ASC',
_IsValidDesc = '_isValid_DESC',
_PublicationScheduledAtAsc = '_publicationScheduledAt_ASC',
_PublicationScheduledAtDesc = '_publicationScheduledAt_DESC',
_PublishedAtAsc = '_publishedAt_ASC',
_PublishedAtDesc = '_publishedAt_DESC',
_StatusAsc = '_status_ASC',
_StatusDesc = '_status_DESC',
_UnpublishingScheduledAtAsc = '_unpublishingScheduledAt_ASC',
_UnpublishingScheduledAtDesc = '_unpublishingScheduledAt_DESC',
_UpdatedAtAsc = '_updatedAt_ASC',
_UpdatedAtDesc = '_updatedAt_DESC',
CategoryIdAsc = 'categoryId_ASC',
CategoryIdDesc = 'categoryId_DESC',
CreatedAtAsc = 'createdAt_ASC',
CreatedAtDesc = 'createdAt_DESC',
IdAsc = 'id_ASC',
IdDesc = 'id_DESC',
TitleAsc = 'title_ASC',
TitleDesc = 'title_DESC',
UpdatedAtAsc = 'updatedAt_ASC',
UpdatedAtDesc = 'updatedAt_DESC'
}