I’m sorry, but I’m not sure I understand your question. Are you looking to upgrade Theia? We don’t really have a browser support policy, so you’ll have to try out whether current versions of Theia run with old Chrome browsers.
After building with the next version, installing the plugin by specifying vsx_registry_url will fail to install
How are you trying to install plugins? The recommended way is to either register their URL in the package.json](Theia - Cloud and Desktop IDE Platform) or to install them manually using the vsx-registry view.