[Mozilla Enterprise] Install location of Flash plugin on Linux for ESR 78 ?

[James Pearson]

I notice the first 'candidate' release of ESR 78 is available via 
http://archive.mozilla.org/pub/firefox/candidates/78.0esr-candidates/

I've installed ESR 78 on Linux (x86_64) plus the latest Flash plugin 
under browser/plugins/ in the Firefox install directory - which is where 
I've put it for all previous installs of ESR - but the plugin is not found

If I put it in ~/.mozilla/plugins/ or /usr/lib/mozilla/plugins/, then it 
is found

So I'm guessing that the browser/plugins/ location under the install 
directory has been removed as a possible location for plugins - anyone 
know why? Is this a 'bug' or a 'feature' ?

Thanks

James Pearson