This was in regards to the Opacity smooth keyframes @Hudson555x reported. Basically, I ask that beta testers help a little further by qualifying their bug reports a little more. Many of bug reports we receive on the beta thread are for old or minor bugs. Again, the beta test period is mainly for finding major regressions and critical blocking bugs. If it helps, think of it as a release candidate instead of beta.
I reproduced the opacity bug, and it is not new. I also have a fix, but I am not going to put it into the 21.02 release. The workaround is to either using only linear keyframes as you have done or to to change only the second keyframe to linear so that the top is flat and does not go over 100%. The interpolation algorithm that all smooth keyframes uses does not provide full control over the curvature. In this case, when the curvature exceeds the filter’s range maximum, the filter misbehaves.