You can uninstall anything, your activation won't be lost. A new activation is required only if you change hardware.
Of course, if you uninstall the Addon Manager as well, no FSDT scenery will work, that's why there's a question about it when uninstalling a scenery, so you know if you do that, even *other* FSDT sceneries will stop working.
If you reinstall a scenery (they all come with an OLD Addon Manager that doesn't work anymore, since Esellerate closed in 2019 ) and try to run the sim without updating the Addon Manager, first not only the scenery will not work ( because the old Addon Manager cannot recognize the new QLM license, since it was made for Esellerate ), but it's possible you'll need to reactivate again, after you update the Addon Manager.
So, always update the Addon Manager last, whenever you need to reinstall a scenery.
