After spending some time researching this issue further, we've identified and created a potential solution for it with the standard fwupd package (APT). However, it would need to be tested more thoroughly to ensure that it fully resolves the issue and doesn't introduce any regressions that would affect the stability of the system in general.
How to test the solution
If you're still experiencing this issue – even after following the steps I mentioned in this post – and you're happy to test pre-production software, you can apply this solution by opening the Terminal (Ctrl+Alt+T) and entering these commands:
sudo add-apt-repository ppa:zorinos/fwupd
sudo apt update
sudo apt dist-upgrade
After installing all updates, please restart your computer to apply the changes.
To make sure that the original stuck firmware update gets installed, you can open the Terminal and enter these four commands:
sudo fwupdmgr refresh
sudo fwupdmgr get-updates
sudo fwupdmgr update
sudo rm /var/lib/fwupd/pending.db
Finally, restart your computer once more to resolve the original issue fully.
Feedback
Please let us know if following these steps to test this solution resolved the original issue for you. In addition, please let us know if you noticed any stability issues with other parts of the system during everyday use after applying this solution.
This information would help us to fully prepare this solution to be potentially included as a software update for all Zorin OS 17 users.