It’s hard to see examples of FOSS being used widely between people. This could be the 2nd time after Mastodon that a FOSS project receives massive attention.
I can’t recall other software that the public might have used without knowing it’s open source. The ones I can get off the top of my head may be Firefox or Inkscape.
there is a trend now : big $ don’t want 3rd party apps any more. May be the next is youtube : block individious, block newpipe…