...

Test Runs archived via Test issue can be restored at any time by restoring the Test issue.

Tests are also hidden from Test Repositories and Test Plan Boards as well.

Archiving Test Plans

Archived Test Plans are no longer used as scope for the Test Run Status and Requirement Status,

Archiving Projects

When archiving a Project its issues are archived as well. If any Test or Test Execution is found, Xray will archive its internal data, namely the Test Runs will be archived and the Tests will be hidden from the Test Repository and Test Plan Boards.

This can be a long running task depending on the amount of Xray internal data to handle. Currently, Jira provides no way of knowing the progress of a project archival. However you can use this:

Xray built-in reports and gadgets

...