It is impossible to update a gesture extension into something that works properly. The APIs don't exist. The workaround is to inject scripts into the page to track gestures, which means gestures don't work until the DOM is parsed, and don't work on about:newtab or other about pages.

Multiprocess had a significant migration period. Webextensions had "Well here's some APIs, we'll try to get you more before the day we switch. Some of the important ones are coming the version after, oops. And some are still missing but suck it up."