Hi, limited knowledge here, so probably not all your questions will be answered..
Sydney wrote: ↑Sat Sep 12, 2020 10:24 am
word such as "jailbreak". And what is ME, by the way ?
Huh? Is anybody "jailbreaking" Thinkpads?

Never heard of it! Heard it used when talking about smartphones.. Usually means to acquire ability to install the software you want rather than the software the maker has limited you too.
Intel ME is Intel Management Engine, pls. look that up online if you want.. It's a bit of software running on your machine that can be seen as providing a backdoor for malicious or perhaps government agents to get into your machine.. At least that's the perception

I know it sounds a bit like like a conspiracy.. The original/official purpose is to make it easier to manage laptops in large corporations I guess. It seems quite sensible for me to want to disable it. 1vyrain offers an option to disable it but there are more radical solutions too.
BTW go into bios and make sure "Computrace" is "Permemantly disabled". That's another backdoor. This time a very real backdoor if gets activated for whatever reason which it rather rarely but apparently can do.
Sydney wrote: ↑Sat Sep 12, 2020 10:24 am
Anyway, I think I understood that IVprep is only to downgrade the Bios before using 1vyrain, but since I currently have a 2013-version I guess I won't need that.
I think you're right to describe this utility as a way to install whichever version you want of the official BIOS. Can go up, can go down in version
Sydney wrote: ↑Sat Sep 12, 2020 10:24 am
Regarding 1vyrain: is there a ELI5 anywhere?
Now you're speaking a cryptic language! ELI5?..
Sydney wrote: ↑Sat Sep 12, 2020 10:24 am
Specifically: what does it do other than to unlock a bunch of features that I do not understand and am not sure I will need ? Or should I need them ? I wish I could share the excitement ! Does it ALSO update the BIOS ? Or do I still have to update the BIOS after I installed 1vyrain ?
Thanks so much for clarifying !
Edit: According to this video
https://www.youtube.com/watch?v=LSFgV_9wVow 1vyrain installs BIOS v. 2.82 (2019-08-07) so I guess it includes the update.
I'll leave to others to advise.. If you don't feel like you need any of the features probably no need to go for the trouble.. Was there something about managing fan noise there?.. Many people think X230 is loud
Sydney wrote: ↑Sat Sep 12, 2020 10:24 am
Still not entirely sure which is the better solution: install a Lenovo-update that I can always downgrade with the help of ivyprep, or install 1vyrain ?
I believe you should still be able to use ivyprep to go back to stock BIOS after you have installed 1vyrain variation of it, though I haven't tried