Steps to Reproduce:

1. take your tablet
2. open => https://m.mediawiki.org/wiki/Template:PD_Help_Page
3. language box is set on english (screenshot 1)
4. scroll down and notice 'Last edited 4 months ago...'
5. scroll up to top
6. language banner appears
7. select french (screenshot 2)
8. notice the URL is unchanged (not /fr)
9. scroll down and notice 'Last edited 4 months ago...'

Actual Results:

• Point 8 : the URL is still the one of the EN root page
• Point 9: last update has unchanged and the french displayed page is not the last one (last is from 4 décembre 2019 à 10:01)

Expected Results:
When using languages from the banner load the last version of the translated subpage (here load https://m.mediawiki.org/wiki/Template:PD_Help_Page/fr) which will update the corresponding 'Last modified ....' automatically