I'm using 18.04 (32 bit) since some time, but I just now tried to write something in Libreoffice. It's completely unusable, just randomly freezes my entire computer so that hard reset is required. One cannot predict on which operation it will freeze. I try to Format -> Paragraph having more than one paragraph selected - opens dialog, then freezes. I try to open a second document in a new window, displays first page of the opened document, then freezes. Even after copying some text from one document to another it freezes!
As I mentioned, the only way to get out of the freeze is a hard reset, so it makes the software just unusable. Which makes the system as a whole hardly usable, because to use a text editor I have to switch to another system, for example my old Ubuntu 10.04, where I NEVER EVER experienced such system freeze.
Has anyone else experienced this? Any hints?
No, never experienced anything like this in all my years of using OO/LO every day, heavily. Maybe remove and reinstall LO? Do you update regularly? This is a strange one...
Hello, I am thinking since you are using a 32 bit ISO, your system might be older and may not have enough resources, What are the specs for your machine?
My machine is a HP XW4100, so it has a Pentium 4 3 GHz CPU and 2 gigs of RAM. However I don't think it's a problem with resources, because in that case the machine usually would gradually slow down and finally become unresponsive. However, even in that case you could usually switch to the text screen with Ctrl-Alt-F1 (this works on a very low level), login in text mode and kill the processes that are causing the problem.
In my case, I get an instant hard freeze, even when the machine isn't doing anything else. And even Ctrl-Alt-F1 does not work.
I would rather suspect an issue with the graphics driver and some interaction between this driver and LO, because I have an old Nvidia card that Nvidia does not support anymore and I can't use a proprietary driver which I used in 10.04, so I'm using Nouveau.
I would bet Xorg (the display server) is locking up. In that situation, the kernel might still running but Xorg is "stealing the keyboard" giving the illusion it's frozen. 
The SysRq key on your keyboard may come to the rescue. At least if you can "take back" the keyboard and go to a console (CTRL+ALT+F1) you can dig out logs for diagnosis.
This article nicely sums up the key combinations:
Also a wiki page: https://wiki.archlinux.org/index.php/Keyboard_shortcuts#Kernel
Writing unsaved data to disk and gracefully restarting is better then a hard restart to prevent data corruption. If the SysRq key combinations doesn't let you get back to a console, at least a graceful restart will write those old logs to disk to find out what caused the freeze, and why LibreOffice. 
Some logs I'd suggest to check:
dmesg
cat /var/log/kern.log
cat /var/log/Xorg.0.logHello raj001
The point about your hardware might be valid. If you can not find a solution you might want to try "MX Linux":
If you can get things working on Ubuntu-Mate that would be good, but if not this gives you an alternative to try. I use MX Linux on a 32bit netbook - it works well in that setting (Atom processor, 2GB RAM). 
I thought I have found a workaround (and wrote a post about it here), but I was too optimistic 
. The lockups still occur, only less frequent.
I tried to disable Nouveau and switch to the regular unaccelerated X server. There are no lockups then, but the GUI is horribly slow without acceleration - watching any video is impossible. So it's not an option. However it proves that the issue is definitely related to the graphics hardware.
Looks like I need to buy a new graphics card anyway, one that is supported by proprietary drivers. However it should not be too new to be supported also by proprietary drivers in old Ubuntu 10.04 - due to the issues described here I still cannot fully migrate off it. I wonder what model should I choose...
This would be the perfect use case for a secondhand card! This costs nearly nothing and you can try some out.
At first, I would try an AMD card. There aren‘t much alternatives to be honest, as I know Intel with CPU integrated graphics chips only.
I have problems with an old NVIDIA card as well on one system. There I have to stick with an older driver. But luckily this one still is supported in 18.04.
Good luck!