This is Geopack.

Geopack is a vanilla-colored Minecraft resource pack based around geometry, geometric shapes, and patterns. The goal is for as many textures as possible to be made into a more abstract and geometric style.

When Minecraft snapshots come out, snapshot edition add-ons will be released. They are marked as alphas for snapshots, and as betas for pre-releases. These must be used over the most recent full release.

Optifine CTM is also supported for various blocks, such as ores, glass, and polished blocks.

Most textures should work down to 1.13. It's also available on PlanetMinecraft (linked above).

If you're this far down, feel free to check the Discord server, also linked above!