I would love if there was an option that would allow while typing in a Cell that pressing ENTER on the keyboard would enter a return character, or a new line, however you want to look at it.
For almost 6 years I've been regularly working with spreadsheets that need new lines in the cell. Even after 6 years CTRL+ALT+ENTER or ALT+ENTER does not seem to be natural to me. I keep just hitting ENTER and I'm sure I'm not alone. My mind never thinks that ENTER should move to the next cell. Moreover, sometimes that other office suite decided to just stop allowing ALT+ENTER to work, one of the reasons I got my company to switch to OOo, and since Libre. I think this enhancement is one more small thing that could help us in the Office Battle.
I'm not sure you still need that help. probably you had found it by yourself.
Anyways, I believe you need to know from
It works on my Ubuntu 14 + Libreoffice 18.104.22.168