I had the same issue, updated today. Got a prompt with all the new KDE features including OCR. But it was missing from spectacle.
Fedora 43 KDE 6.6.0
Fixed it by installing:
sudo dnf install tesseract-devel
sudo dnf install tesseract
It’s possbile to install language packs, find them by using:
sudo dnf search tesseract-langpack