Hi
Maybe it is better to enable it if this error keeps coming back
This is not an error message. What this says is just "this page is a duplicate", so we're not going to index it.
If you add a canonical, it will still be a duplicate (of another page), and it will still not be indexed - because Google thinks it's a duplicate.
Indeed you won't see that "error" message, but that page will not just "silently" NOT be indexed.
I made some 403 redirects to new pages when I updated my site from J3 to J4.
403 is not a redirect, 403 means "Access forbidden". Not sure why you would do that.
In addition, if that page was a 403, then you would not see that error message, because Google would just not be able to access it and determine it's a duplicate.
Best regards
Yannick Gaultier
weeblr.com / @weeblr