Great that there are so many fixes, but so few changes for a new release. Also… hardcoded OAuth tokens is questionable. People connecting Gmail are basically giving Mozilla full access to their email:
https://github.com/thunderbird/thunderbird-android/issues/6176
If there is no fee then sometimes it does hurt your credit to cancel because one factor is average age of total accounts. If you’re just worried you’ll use them cause they are convenient you could literally shred the cards but keep the accounts open.