Self-isolation at own accommodation- subject to PCR. Foreign nationals transiting through Kosovo who leave within 3 hours of arrival are exempt, as are foreign nationals passing through Kosovo by organised transport (i.e. regular bus line), provided they leave within 5 hours.
There are medical staff at border crossings and the airport and you may be subject to a health check, particularly if you are displaying coronavirus symptoms. You should follow the instructions of the medical staff on the border.