firefox XML parsing error

[Bob]

The computer that has this problem is basically a file and print server so I
seldom logon to it.  I tried to use firefox and get the following popup message
during firefox startup.

XML Parsing Error: mismatched tag. Expected: </popupnotification>.
Location: chrome://browser/content/browser.xhtml
Line Number 1791, Column 7:
    </popupnotifkcation>
------^

I deleted the current profile and recreated it.  Same problem.  I then decided
to try and update the system.  That failed with the following message.

Reading package lists... Error!
E: Problem parsing dependency 21 of
gcc-8-aarch64-linux-gnu:amd64=8.4.0-3ubuntu1cross1
E: Error occurred while processing gcc-8-aarch64-linux-gnu (NewVersion2)
E: Problem with MergeList
/var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_groovy_universe_binary-amd64_Packages
E: The package lists or status file could not be parsed or opened.

I then tried the magic incantation of

pkg --configure -a
apt install -f
apt clean
apt auto remove
apt update
apt full-upgrade -y

which did not help.  It failed at 'apt install -f' with the same error.

After some searching of the internet I looked at
"https://askubuntu.com/questions/30072/how-do-i-fix-a-problem-with-mergelist-or-status-file-could-not-be-parsed-err"
which fixed that problem with apt.

After the upgrade firefox still gets the error popup,

Anyone have a suggestion on how to recover from this error?

-- 
Robert Blair


We need leaders not in love with money but in love with justice.  Not in love with publicty but in love with humanity  -- Martin Luther King