https://www.phoronix.com/scan.php?page=news_item&px=NXP-MX8-Mainline-Kernel-Not-Yet says support in the linux kernel for the chip used by the librem5 is not done yet.
Do we know how far away it is?
The last progress report from the Purism kernel/emebedded guys was this I believe: https://puri.sm/posts/librem5-solving-the-first-fsf-ryf-hurdle/
That was a month ago, found the link from a older phoronix article actually: https://www.phoronix.com/scan.php?page=news_item&px=Librem-5-Secondary-Proc-Blobs
So TL;DR: They have to move some initialization code to a secondary processor on the SoC (to comply with FSFs RYF certification) and have been working on that for a month. Sounds like a task which could be completed within a month with some luck so they are possibly able to boot a libre kernel now, but who knows.
If the patches mentioned in the article you linked is not upstreamed before the Librem 5 will be shipped they will likely apply these patches downstream instead, so that should not be an issue unless there’s some critical bug in those patches.
Just found this in the latest blog post, not sure how I missed that
The image built for the i.MX8 board can now boot a very basic mainline kernel (instead of the vendor kernel offered up by the manufacturer). The next steps are to bring more components (like the display) online and to upstream these changes. All in all though, this i.MX8 image is really coming together!
I got today Linux 5.12.1 on Librem 5 (i.MX8) Byzantium