Turning that notion on its head, Pinephone could be one to watch.
They more or less intend to supply the hardware only. This avoids the pretence of vendor updates entirely, by both the company (Pine64) and the ARM licensee (Allwinner).
The software stack is up to you, with mainline Linux support courtesy of the A64 [0] powering a number of 'RPi-killer' boards. Device updates will be supplied by the likes of Ubuntu Touch, LineageOS, postMarketOS et alia mobile distributions.