Good mainline linux support has not been my experience for the kinds of mobile SOCs the Rabbit was inevitably going to be using. Taking a look at the PostmarketOS support page for the mediatek SOC used in the product [0], seems like most of the sleep and radio drivers are not mainlined/supported. Yes, Qualcomm and mediatek drop support after annoyingly few years, but they do provide support before EOL.
Haven't mentioning mainline support at all, and I'm speaking relative to Android: vendors that do Linux poorly do Android even more poorly
And I wouldn't say that these vendors blanket provide support before EoL. I work on a product where EoL is a very long time due to automotive involvement. The vendor's standard of support is extremely low, with most requests resulting in being pointed to some "partner" which is usually a ragtag team of contractors well versed in some set hacky fixes for the vendor's boards
[0] https://wiki.postmarketos.org/wiki/MediaTek_MT6765