>>> Unlock the bootloader, then install LineageOS, MindTheGapps, and Magisk.
Unless you have researched this and are comfortable doing these things, this is not something that's easy to do. I bricked my OnePlus Nord100 not once, but TWICE trying to install Ubuntu Touch.
It happened because the Nord100 shipped with a more current Android version (11.xx) and Ubuntu can only be installed over two very specific versions (10.xx) on the Nord. I bricked it once thinking it could be installed over the 11 version. Then I had to figure out how to reflash the phone back to the 10 version, then run the UBports installer.
I was lucky because I bought the Nord100 for like $50 on ebay so it wasn't a big deal if I wasn't able to unbrick the phone, but if you do this to a more expensive phone, the consequences are a lot more expensive.
I love Lineage OS and have it running on a Pixel 4XL, but my experience flashing and re-flashing the phone several times, and all the work I went into just to get UT running on that phone, really dampened my enthusiasm to ever do this again.
Do I misunderstand what Ubuntu Touch is? I thought it was its own thing whose only relation to Android was the BSP, not some type of layer on top of Android. If so then it seems irrelevant and unfair to bring up w/r/t the well-tested Android-to-different-Android path.
Unless your phone has full mainline kernel support (pinephone, librem 5, pocophone f1 etc...), All these Linux on phone projects mostly use Android system services (init, surfaceflinger, rild etc..) to talk to the device hardware, without bringing up the Android UI.
They do this so that they don't have to reverse engineer and write the hardware drivers from scratch and simply use Android's user space drivers for them.
I haven't been involved in that domain for a while, but it basically meant reusing the contents of your device's /system and /vendor partitions and simply installing the Linux OS into /data.
Unless you have researched this and are comfortable doing these things, this is not something that's easy to do. I bricked my OnePlus Nord100 not once, but TWICE trying to install Ubuntu Touch.
It happened because the Nord100 shipped with a more current Android version (11.xx) and Ubuntu can only be installed over two very specific versions (10.xx) on the Nord. I bricked it once thinking it could be installed over the 11 version. Then I had to figure out how to reflash the phone back to the 10 version, then run the UBports installer.
I was lucky because I bought the Nord100 for like $50 on ebay so it wasn't a big deal if I wasn't able to unbrick the phone, but if you do this to a more expensive phone, the consequences are a lot more expensive.
I love Lineage OS and have it running on a Pixel 4XL, but my experience flashing and re-flashing the phone several times, and all the work I went into just to get UT running on that phone, really dampened my enthusiasm to ever do this again.