I don't have an accurate idea about the official guidelines, but yes, a friend of mine is currently traveling in Uttarakhand, so I guess you can visit there also
I checked out with my friend who is from Uttrakhand, he said if you're visiting uttrakhand come with your own vehicle only right now. And as mentioned everywhere, you need to have RT-PCR report+ epass to enter.
हिमाचल प्रदेश ने दूसरे राज्यों से आने वाले पर्यटकों के लिए कोविड निगेटिव जांच रिपोर्ट की शर्त हटा दी है, जबकि उत्तराखंड में बाहरी राज्यों से आने वाले पर्यटकों के लिए आरटीपीसीआर निगेटिव रिपोर्ट व स्मार्ट सिटी पोर्टल पर पंजीकरण अनिवार्य है।
You can visit upto rishikesh only.. after that you need rtpcr report of within 72hrs to go further on mountains. but right now borders are sealed till 21june.
For uttarakhand u need a covid negative test report that is not older than 72 hours. Do register yourself and get an e-pass to avoid any inconveniences.