Halo Infinite's multiplayer just dropped today, three weeks early. Very cool. And with the Campaign coming on December 8 we've got a detailed breakdown of what you'll need hardware-wise to explore and Big Team Battle on Zeta Halo. In terms of recommended GPUs, developer
343 Industries puts the AMD Radeon 5700 XT and the NVIDIA GeForce RTX 2070 as the rendering weapons of choice.
To play on Ultra (4K) you'll need a bit of a beast, not only in terms of GPU (a Radeon RX 6800 XT or GeForce RTX 3080) but also CPU with top of the range Intel and AMD CPUs listed.
Specifically for the Multiplayer that's dropped today you'll need 26.42 GB of HDD space, with an additional 7.68GB for High Res Textures -- that is, for those that play in 1440p or 4K.
Halo Infinite PC Hardware Requirements
Low (Minimum)
OS: Windows 10 RS5 x64 (October 2018 Update)
CPU: AMD Ryzen 5 1600 or Intel i5-4440
GPU: AMD Radeon RX 570 or NVIDIA GeForce GTX 1050 Ti
VRAM: 4+ GB
RAM: 8+ GB
Storage: 50+ GB
Medium
OS: Windows 10 19H2 x64 (November 2019 Update)
CPU: AMD Ryzen 5 2600 or Intel i5-9500
GPU: AMD Radeon RX 5500 XT (8GB) or NVIDIA GeForce GTX 1660 (8GB)
VRAM: 6+ GB
RAM: 8+ GB
Storage: 50+ GB
High (Recommended)
OS: Windows 10 19H2 x64 (November 2019 Update)
CPU: AMD Ryzen 7 3700X or Intel i5-9700K
GPU: AMD Radeon RX 5700 XT or NVIDIA GeForce RTX 2070
VRAM: 8+ GB
RAM: 16+ GB
Storage: 50+ GB
Ultra
OS: Windows 10 19H2 x64 (November 2019 Update)
CPU: AMD Ryzen 6 5900X or Intel i5-11900K
GPU: AMD Radeon RX 6800 XT or NVIDIA GeForce RTX 3080
VRAM: 10+ GB
RAM: 16+ GB
Storage: 50+ GB
Based on the fairly high specs we assume the base Xbox version will be similar to the Low specs.