Tested against pr10093. Install strimzi operator, choose version 0.19.0 and manual approval strategy, then switch channel to strimzi-0.20.x, now there is update available. Check status card on overview page, in Operators field the upgrade info and icon are shown correctly.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (OpenShift Container Platform 4.7.36 bug fix update), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2021:3931