Thanks to the recommendation on this boards, I just booked the Yukon Klondide Adventure excursion with Chilkoot Tours for July 30.
Prior to booking I noticed that their website shows the 8:30 AM tour was not available. They normally have 2 options: 8:30 and 9:30. So I called and spoke with Stacy (the owner). It turned out they had to cancel the 8:30 tour and combine it with the 9:30 since they only have a few passengers booked. Stacy said that lot of passengers called and told her they wanted to cancel because they don't want to take a COVID test for this excursion. She said the testing requirement is killing their business, but unfortunately many visitors are not aware that they don't need to test to enter Canada anymore.
If you are interested in this your and would like to do the 8:30 excursion, please add a note in the comment section. If they have enough passengers interested in the 8:30 trip, they would move the tour to 8:30. As of now, only the 9:30 slot is open for booking. It's sad to hear these business still suffering from COVID. I hope her company will have more customers soon.