SailfishOS supports a wide range of Sony Xperia devices, including the 10 III that I own. They seem to have done a pretty stellar job in booting a Linux kernel with working drivers, but I'm less hyped about their userland.

That got me thinking, would it be possible to run a different Linux userland on the SFOS kernel?

Like, can I basically build an Ubuntu rootfs and use SFOS boot and system partitions, or something along these lines?

I'm a software developer who knows C, has cross-compiled software, developed Android apps and embedded software, ran custom Android ROMs and SFOS, compiled custom kernels, etc. I'm not quite a kernel developer but I think porting Linux to a device already running Linux should be within reach?

Of course ideally SFOS would mainline their drivers and everything would be super straightforward, but my understanding is they did not do that, and duplicating their effort or shepherding their code upstream is not something I'm planning to do at the moment.

The typical approach of porting Ubuntu appears to be to start with Gallium which to my understanding is an abstraction layer between a LineageOS system image and a generic Linux driver. Sony Xperia 10 III is already not supported in LineageOS, so this path also seems infeasible.

SFOS is already booting Linux on the device, so you'd think it's a matter of "just" replacing some binaries. But I could use some pointers on the logistics and architecture.

For example, does the system image / rootfs map cleanly to kernel and userland? Like, do the initramfs and all the kernel modules live on the system image? If so, can I just literally download and flash a generic aarch64 rootfs? Maybe I need to extract some kernel modules from the SFOS rootfs? Are there any user mode bits that are device specific that I need to know about?

I have read that Sailfish OS is working on support for the mark three, expected to be released in early 2022. Therefore I've bought a mark three device instead. The same question still holds: what does it take to add support for it?

I've also read a bit more of the guide, which seems to assume your devices is supported in LineageOS and TWRP, which it is not. Does that mean I'd first have to contribute support to TWRP and LineageOS?

I did see reports that people successfully run GSI on the device, so does that mean it should also work with the Gallium GSI?

Hey, I'm a developer with... some experience poking at kernels but new to porting Linux to phones.

I noticed @HengYeDev maintains a port for the mark one, and I am wondering what it'd take to support the mark two?

From reading https://docs.ubports.com/en/latest/porting/introduction/Intro.html it would seem that being an Android 10 device it should work with GSI Gallium, but over at PostmarketOS it's listed in the non-booting category: https://wiki.postmarketos.org/wiki/Sony_Xperia_10_II_(sony-pdx201)

It does appear to be supported by Sailfish OS. Does Jolla upstream their drivers and stuff? I'm guessing that would help.