Vizio has released a major firmware update for its 2020/21 OLED and P-Series TVs with fixes for HDMI 2.1 4K120, 4K60, VRR, and HDR issues together with PS5, Xbox, and Nvidia cards.
Vizio's HDMI 2.1 update
If you own one of Vizio's 2021 high-end TVs (formerly known as Vizio's 2020 TVs) connected to a PlayStation 5, Xbox Series X or the Nvidia RTX-3080, you should check if there is a new firmware available for their TV.
The company's latest firmware includes a list of fixes and improvements related to HDMI 2.1, specifically 4K120, 4K60, VRR, and HDR:
Sony PS5: Improved [email protected] support
Sony PSS: Enhanced [email protected] RGB FRL with HDR support
Added support for Nvidia PCs at [email protected]
Improved support for [email protected] VRR on Xbox Series X and Nvidia RTX-3080
Updated support for HDMI Forum VRR

The firmware is rolling out now for Vizio's OLED TVs, 2020/21 P-Series Quantum X, and 2020/21 P-Series Quantum models.
It also includes support for individual IR codes for HDMI inputs, compatibility fixes for AV receivers and Xbox audio, and more.
The full changelog (via The Verge) is included below.
Vizio's firmware ver. 5.10.15 - changelog
Compatible Vizio 2021 TVs
FlatpanelsHD FlatpanelsHD - Source: The Verge