It's time for a mid-2019 lore update check-in!
I usually post this at the end of the year, but to heck with it, let's see how the lore overhaul is progressing.
To qualify for this list, you simply need to lack an up to date extended bio. We're now at a point where the majority of champions have reached this point. Note that a few of these, like Jax or Rek'Sai are in the weird position of having a short story but no extended bio. In a few of these cases, like Vel'Koz, these short stories can change as the character receives updated lore.
With that in mind, here is who we have left to update. I am excluding Fiddlesticks/Volibear from this list as their VGU's are confirmed, so I am counting them as done for all extents and purposes.

These two don't count, but as their bios were among the first released during the lore overhaul phase, they're criminally short and deserve more IMO.

That's a pretty small list. When I last did this, we were at 38/142 left to update. As of now, we're down to 27/145, around 18%. We've also added 3 champions since then, as previously mentioned.
By region, the numbers left look like this. Freljord: 5 Bandle City/Yordles: 6 Void/Icathia: 6 Demacia: 2 Zaun: 2 Noxus: 2 Ixtal: 1 (now that Malphite has been moved to it). Other: 3
It gets smaller and smaller fellas. Notably, the Void/Icathia remains consistently untouched. This means that, from what we had prior and including Fiddlesticks/Volibear, Riot has updated the lore of 11 champions since the start of the year. A bit slower paced than last year, but any progress is still worthwhile, and these consistent lore patch notes really help to keep track of all this.
Edit: Forgot Talon, woops. Also took off Udyr, he's already done.
and
are probably going to get minor passes to integrate them into Ixtal
lore update just in, woohoo.