Not sure what updates you are expecting to happen.
I’m not aware of any effort trying to identify the traffic going in and out on Thunderbird under android. The guesses from the one reporting about what happens when configuring a new email account is of no use since it’s easily associated to Thunderbird looking for ways to easy automation on new accounts settings.
Unless there’s a throughout analysis of the traffic, I’m not aware of anything to be expected. You can try reaching the one reporting his concern, and ask if he has looked into how to report an actual issue/bug to Thunderbird, or if someone else has done it
Yup, divestOS allows for booloader lock though unfortunately they don’t support microG. I hope they somehow help upstream their relock solution to LOS. I use LOS for microG instead, since I need stupid bank apps and also for the office some stupid proprietary multi factor authentication apps… If only LOS for microG could lock the bootloader at will (it needs to be unlocked for major upgrades, like on regular LOS), that’d be great.
There’s as well CalyxOS, which uses microG and also locks the bootloader, however I do prefer LOS since the strategy from CalyxOS and GrapheneOS trying to deGoogle pure Android in my mind sound like having some limitations, as opposed to LOS approach to be based on AOSP instead. Though that’s just in my mind, I’m sure those guys in Calyx and Graphene are the best at security and privacy.