OK, it's official, as of Oct. 1 there are no Covid restrictions for entering Canada.
So, even if picking up at Sumas, it's no big deal to visit ETI beforehand or cross back into Canada to do some sightseeing or take the Northern route East.
It's important to note that the US government has not changed their rules. Unvaxed US citizens are allowed to cross into the US, however Canadian (and other) citizens must be prepared to present proof of vaccination. A covid test is not required when entering by land or ferry. https://www.dhs.gov/news/2021/10/29/...elers-enter-us