It was updated automatically for me, both on Firefox desktop and Firefox for Android.
When I publish a new version of uBO, I deploy gradually, starting with 5% of users then increasing every day: 12%, 25%, 50%, 100%."
UPDATE
After reading the comments on the linked blog article, frantically hitting the "Update" button (in developer mode) many times indeed helps! I had clicked it quite a few times already, but "normally", going crazy and hitting it a lot and quickly indeed lead to the update occurring.
Wow, what a crazy user interface that requires users to go berserk on the buttons...