It’s called GeneratePress. I’ll tell you more about it soon.
— UPDATE Jan 8, 2020 —
Sorry it took so long for this update! I’ve been having a blast hacking and slashing Generate Press! Customizing this theme is a little different, because it doesn’t rely as heavily on template file replacement, but is more OO than other themes I’ve played with. And it supports any page builder, so you don’t even have to dig into the files to come out with a great looking, lightning-fast website.
This site is built using it, and I have a few others in development right now. The pro version is totally worth the low cost, as it unlocks loads more features.
The only complaint I have is that modifying any blocks in the pro version requires the use of a plugin file. For example, I wanted to modify the secondary nav block on JustJenna.net, so I had to create a must use plugin called “richards-gp-mods.php” containing the function(s) to overwrite. This is due more to WordPress’ order-of-operations (loading plugins before themes) so I had to get the functions defined in a plugin before the other’s loaded, otherwise it was already defined.
GeneratePress does a good job of keeping all of their functions wrapped in if-not-exists clauses, so as long as you know when the function loads, you should have no problem overwriting it.