Trying to plug a four year hole of missing data when my wife ragequit G+ in May 2016 after we hired moot of 4chan fame. Lots of 1:1 posts gone :(
Luckily she didn't downgrade Hangouts, so I still have those 28k messages between us.. (Many of which are "the gbus is running late, again")
We did migrate to Matrix.org that month and I do have all of that...