No such package exists in the repos or the AUR.
Again true for webkit2gtk-5.0.
electron19 and zoom are both in the AUR though.
The first 2 definitely need to go, and if you arent using the AUR, dont need these packages, or have no idea what I am talking about … then all of them should be removed.
The purpose of checkrebuild is to scan your system for packages that need to be rebuilt.
When system libraries are updated … certain unsupported, foreign, manually-installed software may need to be compiled again against the new libraries. Such as AUR packages. checkrebuild is telling you which of your packages this applies to.