The official Adobe Flash player download link is:-
https://get.adobe.com/flashplayer/
When you go to that link there is an 'Optional Offer:' section in the centre of the page. Wait a few seconds until the 'Optional Offer:' area displays some offers and then uncheck / untick the box(es) next to the offers to decline / disable them and then click the 'Install now' button.
By declining any offers, Adobe Flash player should be the only item that gets installed.