Xubuntu 20.04 disaster

[MR ZenWiz]

I need some urgent help here.

After I tried to set the preferred applications on my partner's Dell
laptop, I thought perhaps a software update would be wise.

I ran:

sudo apt -y update
sudo apt -y full-upgrade

All seemed to go well, although there was an error message that looked
harmless enough and I let it go (and don't).

I ran the Software Updater, which updated by removing an older kernel
installation, then said I should reboot.  The two kernel it left
behind were 5.4.0.53 and 5.4.0.54.

Since then, nothing works, in either kernel.  The system only comes up
in emergency boot mode, and a df check shows that the /home filesystem
is completely empty - all her files are gone.

We have a backup from a month or two ago (yes, I know - do it more
often), and we can fall back to there if need be, but I have to say
that this happens too often (radical problems with an update or
emergency reboot) for me to want to continue to use Xubuntu on her
laptop at all.  I never see problems this drastic with my desktop, and
I just don't understand what's going wrong here.

I don't have time to go through how to re-enable the wifi from the
command line - I used to know but it's been long enough that I have to
look it up, and I'm frankly sick and tired of having to go through all
this work, even once a month, just to have a system that runs normally
and reliably - two of the reasons I use Linux to begin with.

If I have to reinstall everything I'll probably go over to Linux Mint
because their system is just plain easier to use (for my partner's
laptop - I don't like Mint and my Xubuntu works fine - so far).

Any positive suggestions would be welcome.  I apologize for letting
out my frustration like this, but I have to leave for PT and can't
even follow up for an hour or so.

Thanks in advance.

Mark