rain There were some tiny changes to how exclude works, but in your case, you seem to have some wrong code or it got corrupted at some point ... You have double backwards-slashes \\ where the first means escape, and the second therefore becomes a valid character to search for in the match ... You are therefore trying to match something like \/mytest which is never gonna match anything of course.
As far as I can see, your code should look like this:
'dirs_exclude' => '/(\/|^)(mytest|\.well-known)(\/|$)/',
(\/|^) starts with /slash path name or the actual path name (relative from root)
(mytest|\.well-known) the two paths to match
(\/|$) path ends with slash/ or ends with actual path name
There are shorter versions that would work, but the above makes sure to not block dirs that might be valid, for example mytestsomething or .well-knownsomethingelse.