You're seeing this page because Tridactyl thinks you ran the fixamo command at some point. This command changed two preferences in your user.js file: extensions.webextensions.restrictedDomains and privacy.resistFingerprinting.block_mozAddonManager. Mozilla reviewers think these settings are very dangerous and should never be changed by end users. They gave Tridactyl maintainers an ultimatum: either remove the command and the changes it made to user's files before october 2019 or be blocked.

Tridactyl maintainers reluctantly complied and Tridactyl has restored the restrictedDomains preference to its original value in your user.js. It also added a new preference named tridactyl.unfixedamo in order to know that it shouldn't touch your extensions.webextensions.restrictedDomains setting ever again.

You can find more information here.