By user request, this version of TenFourFox also restores the old general.useragent.override.* site-specific override pref feature. This was removed in bug 896114 for performance reasons and we certainly don't need anything that makes the browser any slower, so instead of just turning it back on I also took the incomplete patch in that bug as well and fixed and finished it. This means, in the default state with no site-specific overrides, there is no penalty. This is the only officially supported state. I do not have any plans to expose this feature to the UI because I think it will be troublesome to manage and the impact on loading can be up to 9-10%, so if you choose to use this, you do so at your own risk. I've intentionally declined to mention it in the release notes or to explain any further how this works since only the people who already know what it does and how it operates and most importantly why they need it should be using it. For everyone else, the only official support for changing the user agent remains the global selector in the TenFourFox preference pane (which I might add now allows you to select Firefox 68 if needed). Note that if you change the global setting and have site-specific overrides at the same time, the browser's behaviour becomes "officially undefined." Don't file any bug reports on that, please.
Finally, this release also updates the ATSUI font blacklist and basic adblock database, and has the usual security, certificate, pin, HSTS and TLD updates. Assuming no issues, it will go live on December 2nd or thereabouts.
For FPR18, one thing I would like to improve further is the built-in Reader mode to at least get it more consistent with current Firefox releases. Since layout is rapidly approaching its maximum evolution (as determined by the codebase, the level of work required and my rapidly dissipating free time), the Reader mode is probably the best means for dealing with the (fortunately relatively small) number of sites right now that lay out problematically. There are some other backlogged minor changes I would like to consider for that release as well. However, FPR18 will be parallel with the first of the 4-week cadence Firefox releases and as I have mentioned before I need to consider how sustainable that is with my other workloads, especially as most of the low-hanging fruit has long since been picked.