As this came up multiple times: phosh 0.20.0 currently requires GTK animations to be on:
gsettings set org.gnome.desktop.interface enable-animations true
So if you (or your distro) turned it off please enable it before updating as otherwise you won't be able to use the overview.
I know animations are on by default in #pureos and #debian so nothing to do there.
Issue: https://gitlab.gnome.org/World/Phosh/phosh/-/issues/818