Super useful package by the way!
I have my own custom impersonation functionality and don't need the 404labfr package.
I have forked the package and removed the requirement for the 404labfr package and it's working nicely, so if I could suggest adding an interface with the required methods:
clear
findUserById
isImpersonating
leave
And can then it's possible register the 'impersonate' service with those methods and any custom impersonation service can be used.
And a suggestion to use the 404labfr package by default.
If this is something you're interested in adding, I'm happy to make a PR.