When Thunderbird starts up, all folders and sub-folders open up. New install on new disk. Old copy rarely did.
Since loading a fresh copy of Thunderbird on a new bigger disk on my Ubuntu laptop, whenever I start it up it opens up all my email folders and sub-folders. I have lots, and it takes time to collapse them all manually. I monitor two other email accounts for a club which also have quite a few folders and sub-folders - same happens on all of them. This did happen occasionally with my old version, but happens every time now with 140.7.1esr (64-bit) running under ubuntu-snap-build - 1.0.