Babyload856

I am using Ubuntu 20.04 LTS.
Of course, as usual, after a Thunderbird update calendar add-ons stop working and I really do not have time to deal with this.
Therefore, I'd like to go back to version 68.12.1 and stop Thunderbird from further updates, but did not find out how to do that.
Please do not try to convince me of staying with the newer versions. I am just tired of these problems and spent an hour or so with fruitless efforts to go back. If I can't manage to roll back, I will have to switch to MS Outlook. No attractive perspective.. but hopefully not inevitable.
I found the release notes of thunderbird here: https://www.thunderbird.net/en-US/thunderbird/releases/
But there is no chance to download.
What I also found is this source: https://ftp.mozilla.org/pub/thunderbird/releases/
Finally, I will probably have to exclude Thunderbird updates from the repository, but did not manage to find out how. Can I select it somehow from 'Canonical partners'?
Thanks in advance for your support!

Hello,
I'm running Ubuntu 20.04LTS on a dual boot system (Windows 10 that i rarely use).. that i have been using for quite some time (back to at least Ubuntu 12-14 or so), and haven't really had too many issues with.. a few here and there, that i've been walked through via ubuntu help groups.
So here is my problem, at some point in allowing automatic upgrades there must have been a glitch, tho i'm not sure how it happened. If i just allow a default boot, i'm unable to access my wireless network, or a few different options under settings. I can't even shutdown via 'power off'. In order to get a working system, i have to select advanced options in Grub, and select Linux 5.4.0.54 (i'm assuming that is the kernel version, please correct me if i'm mistaken).. the latest available on my system in that menu is 5.4.0.62 (i've also stopped allowing updates to happen, tho i allowed a few after i noticed the issue initially).
I'm assuming i might need to rollback the updates, and then update again??
Tho i don't often have time to explore as much as i'd like to, i'm actually running linux with the idea of learning more about it (well ,and the fact i'm not a fan of windows as well). i'm comfortable using terminal, and have installed software both in the gui program 'software' and via apt-get install.
So i'm hoping to get help with both what to do, and why i'm doing it at the same time. If there is any other data needed, or any actions i need to perform, then please let me know.
Your time, attention and help is much appreciated.
-bw