The i.MX 8M Quad has Android drivers and I suspect that the other components in the L5 also have Android drivers, but it would take a huge amount of work to port the L5 to a AOSP-derivative, and you would probably need Purism to help you get the Android drivers for some of the components since they aren’t publicly available. Porting will be much harder than a normal phone, because the L5 uses a lot of non-standard parts (like kill switches and a smartcard reader) that would require a lot of work.
By the way, the lead GrapheneOS developer goes out of his way to publicly criticize the L5 as having insecure hardware, which forestalls any collaboration on that front. CalyxOS may be open to the idea, but they only work on porting to phones which already run well on LineageOS > /e/, so you would have to start there.