Configuration 

What the sets contain 

This extension ships six content elements, so it ships six component sets and one aggregate set that depends on all of them.

All six are driven by one Extbase plugin, so they share one TypoScript block, plugin.tx_academicpersons . That block is shipped once, in Configuration/TypoScript/Default/, and every component includes it. Which component sets a site names therefore decides which content elements the backend offers, not how much TypoScript is loaded.

Every component set depends on fgtclb/academic-base-ctype-group, the set of EXT:academic_base that labels the content element group all academic extensions sort their elements into.

The site settings of this extension — the detail page, and the default grouping, sorting and pagination of a profile list — are declared with the aggregate set. A site that depends on a single component set still gets the shipped defaults, but can only override them in Site Settings when it depends on fgtclb/academic-persons.

Restrict the backend contract selects 

Two backend fields let an editor pick a contract: the Contract of a page contact record of EXT:academic_contacts4pages, and Selected contracts of the Profiles: Selected Contracts content element. Both offer every contract of the installation — in an installation with more than one site, that is every site's contracts, each labelled with a person's name.

Page TSconfig restricts a field to the pages the contracts of that page tree are stored on. Page TSconfig is inherited down the page tree, so each site configures its own folders on its root page.

The setting is opt-in, and without it nothing changes. Respecting the Extbase storage page instead is deliberately not done: a page tree without an explicitly configured storage page would get an empty select and no error.

Set them on the page record of the site root, tab Resources, field Page TSconfig. The path of the FlexForm field is the longer one: it carries the data structure identifier and the sheet, and the dot in the element's name is escaped.

# The "Contract" field of a page contact record.
TCEFORM.tx_academiccontacts4pages_domain_model_contact.contract.itemsProcFunc {
    storagePids = 42,84
    recursive = 1
}

# The "Selected contracts" field of the content element.
TCEFORM.tt_content.pi_flexform.academicpersons_selectedcontracts.sDEF.settings\.selectedContracts.itemsProcFunc {
    storagePids = 42,84
    recursive = 1
}

A contract the record already references stays selectable even when it is stored outside the listed pages. Without that, opening and saving the record would drop the relation, because a select offers no other source for its value.

The restriction is applied before \FGTCLB\AcademicBase\Event\ModifyTcaSelectFieldItemsEvent is dispatched, so a listener of that event still has the last word.

The content elements are hidden by default 

EXT:academic_persons hides all six of its content elements for the whole installation and brings them back per component. Whichever of the two mechanisms below you use, it is what makes an element selectable in the backend again — without one of them the content element is not offered, and existing records keep rendering.

Include the site set 

On TYPO3 v13, add the set to the config.yaml of the site that should offer the content elements:

 base: 'https://example.com/'
 rootPageId: 1
+dependencies:
+  - fgtclb/academic-persons

See also TYPO3 Explained, Using a site set as dependency in a site.

Include static templates 

For an installation that configures its frontend through sys_template records — which on TYPO3 v12 is every installation — the same files are registered as static templates and as selectable page TSconfig files.

Do not combine both 

This applies to TYPO3 v13 only, because v12 has no site sets to combine anything with. A site that uses the site set and the static template reads the shipped files twice. The site set is applied before the sys_template record, so the second read happens after the site settings and after config/sites/<site>/constants.typoscript — and it resets every constant the extension ships a default for back to that default.

Nothing else is damaged: the Constants and Setup fields of the sys_template record, the page TSconfig of a page and the page TSconfig files selected on a page are all applied afterwards and still win. Use one mechanism per site and the question does not arise.