So for x86 …
The crimson repo is there now. I have no idea whether it will successfully upgrade from byzantium to crimson.
The crimson .iso is there now.
(Librem 11 tablets are shipping with crimson pre-installed now.)
It should go without saying that if you are thinking of putting crimson on your Librem 15
- you have a bootable Live Boot USB, and
- you have a suitable backup of the current contents which you know how to restore if you have to
and of course since you would be on the bleeding edge, you would have a Plan B.
I would guess that if you have a spare external disk, it may also be an option to install fresh on the external disk - as a way of testing things out.