According to Canon Japan official website, Canon may release a firmware update for Canon EOS R5 (B&H/Adorama/Amazon) in near future. This new firmware for EOS R5 may add FHD at 120p, Canon Log 3, and low bitrate mode to RAW & IPB for all resolutions and frame rates.
From Canon Japan:
Regarding contents under consideration for correspondence with firmware upgrade
- Full HD/120P recording size support
- Added low bitrate mode to RAW and IPB for all resolutions and frame rates
- Canon Log 3