Manifest v2 is a bit tricky, because there are really three changes overlapping with each other:
- Manifest v3 site permissions changes
- Removal of protected APIs (like the blocking version of chrome.webRequest)
- Chrome Store code review changes that prohibit remotely loading sources
For now, you can either do nothing (as the rollout is not yet complete), or set the ExtensionManifestV2Availability policy to 2, which will still allow Mv2 extensions to be loaded.
That looks something like this on Linux:
echo '{"DefaultBrowserSettingEnabled": false, "ExtensionManifestV2Availability": 2}' > /etc/chromium/policies/managed/default_managed_policy.json
Apparently there's a registry key on Windows? There are plenty of guides out there.
At the moment, the only thing I can find in Chromium that uses that preference is some code that reports to Google on the impact of disabling Mv2.[1]
The other option is to follow their issue tracker and git history, and just revert whatever patches you don't like.
1: https://source.chromium.org/chromium/chromium/src/+/main:chr...