Lubuntu won't boot, stuck at initramfs

Question

I'm a casual Lubuntu user. I installed it a few years ago on an old laptop to keep it working. Pretty sure it was the 18.04 version.

Today, while trying to install WaterFox, I rebooted the laptop via terminal. It stopped rebooting correctly.

First of all, when I start the PC, I get

error: failure writing sector 0x19b802 to `hd0`

Press any key to continue...

Then, after a few seconds, I get the Lubuntu loading screen, which brings me to

BusyBox v1.27.2 (Ubuntu 1:1.27.2-2ubuntu3.4) built-in shell (ash)

Enter 'help' for a list of built-in commands

I searched for solutions, tried:

(initramfs) exit

And got

fsck exited with status code 12

The root fylesystem on /dev/mapper/lubuntu--vg-root requires a manual fsck

I then tried

(initramfs) fsck dev/sda1

And got

fsck from util-linux 2.31.1

I then

(initramfs) reboot

And I got back to

error: failure writing sector 0x19b802 to `hd0`

And the loop continues lol. Any suggestions?

I don't care about losing the data on the PC. I just want it fixed ASAP.

The day after tomorrow I'll be able to use another PC to download Lubuntu on a pendrive (I'm typing from a phone), but if there's a way to fix it sooner please tell me.

UPDATE

tried

(initramfs) fsck -py /dev/sda1

I got the usual

fsck from util-linux 2.31.1

I also tried

(initramfs) fsck.ext4 /dev/sda1

Which gave me

e2fsck 1.44.1 (24-Mar-2018)

fsck.ext4: No such file or directory while trying to open /dev/sda1

Possibly non-existent device?

UPDATE #2

I tried

(initramfs) fsck -p /dev/mapper/lubuntu--vg-root

It run a few hundred lines of something and then spit out

/dev/mapper/lubuntu--vg-root: ********** WARNING: Fylesystem still has errors **********

UPDATE #3

Any attempt to fix the filesystem through initramfs commands has yeld no results.

I found my Lubuntu 18.04 pen drive and booted the installation interface by changing the BIOS boot hierarchy. Over time I put other stuff on the pen drive, but the self-check option from the installation menu tells me that the Lubuntu copy is fine.

I managed to boot the Lubuntu trial version from the pen drive and it seems to work.

I tried to run SMART test from there. I tried both the short and the long test, they both tell me in an instant that the hard drive is ok (which raises suspicions about the test not running at all).

I tried installing Lubuntu but it freezes at a certain point of the installation. The cursor becomes a spinning wheel and it just keeps spinning. I can close the installation and keep using the trial version, but there's no way to go on with it.

I re-tried multiple times, switching my installation choices, but the outcome is always the same. I even tried to install it from the boot menu, without opening the trial version, but it's all the same.

I tried this:

Ubuntu 18.04 installation problem

up to point 5, but I still can't install it.

I need this PC to work. What's the least expensive line of action now?