My reply concerning LineageOS is actually related to the meanwhile closed topic
in which @Douwe gave an important statement which was:
That is a major point maybe not only for people like me.
A lot of discussions about problems, misbehaving apps etc. with FP2 was/is going on in this forum.
To react quickly and give support and also clear verified bugs shortly I think it is best to pre-install a (custom) made OS to such a product and keep its development in-house. Depending here on a third party which should deliver the essential OS could cause delay and bear the risk to scare customers off if it is known that the OS is too buggy and fixes takes too long. Probably the third party would also work on software for other business customers and not only focus on FP. So resources would not only be reserved for FP issues.
Having bought an expensive device that turns out having a buggy and unstable OS causes massive dissatisfaction anyway.
Occasionally I catch up a thread here where again someone reports a problem with an self-installed free alternative OS. Sometimes a small bug, but also essential faults. A company cannot generally expect each customer to puzzle out each problem with the purchased product. What for the pay if it´s not working the customer may think.
So as @Douwe wrote “…working out of the box”.
Imho FP had a good start with its FPOS, and FP done well with its decision to deliver the OS itself and keep development in-house and still offer another free Open OS too.
Also its open business mind allows users to self-install other OS on the platform without loosing warranty, and this is not very common these days.