Tablet Mode not working on Essential Phone (smallest width > 480)

As described at support.mozilla.org/en-US/questions/1222672, Firefox for Android should use 'tablet mode' (tab bar and back/forward/reload buttons) when the 'smallest width' value in developer settings is greater than 480. This has always worked for me on other phones, but on my Essential Phone, it stays in 'phone mode' regardless of the setting. Other apps that change layout based on this setting work fine. There is an Xposed module that can force Firefox to use tablet mode, but I was wondering if there's some other solution to this issue. Thanks a lot for any help!