TL;DR
- Samsung seems to have removed filters from the video mode with new One UI updates.
- The option still shows up in photo mode, but video mode no longer has filters in One UI 8.5 or the One UI 9 beta.
- However, there are some workarounds, including applying filters after recording or enabling filters in photo mode, and long-pressing the shutter button to record a video.
Samsung has been rolling out One UI 8.5 and One UI 9 betas to more devices every week. While the updates bring several new features, it seems that the company might be removing some features as well.
According to several user reports, video filters are nowhere to be found on some Samsung phones since the One UI 8.5 update (via PiunikaWeb).