It’s not officially supported, but I can see a few “unofficial” community builds. I like the idea of getting a small phone as a media player. I have some experience with installing operating systems, but never a phone. How difficult is it? Is this a good idea?
I think its a cool little project. If you like tinkering and screwing around with tech just go for it. But there are few things which come to my mind. Dont take them as advice against it more like pointers and things to think about.
As much as i miss them as a common feature in todays phones. Headjacks on phones were most of the time kind of shit. I had 30€ mp3 players which provided better audio quality than the Z1 compact i had at the time. Idk if the XZ1 got way better? I think the issue is that most phones had terrible D/A converters. But dont quote me on that. But this is only a concern if you have high standards for audio quality for wired headphones. If you use something with bluetooth the point becomes irrelevant. LG V series phones were really good in that aspect and also pleased the audiophiles. They are much bigger bricks though. If you want to use it mostly for audio a used mp3 player might also be a way to go because they can be even smaller.
Installing customroms isnt that hard if you can follow a guide and you are able to use a searchmachine on your own. But its still easy to mess up. I messed up quite a lot over the last 15 years. But atleast my mistakes were always recoverable. Just dont rush things. Take your time. Read up as much as you can before you start the process. Biggest issue i see that there isnt an official build for lineage. With that also no official documentation/install guide which you could just follow religiously. My experience is that those builds provided on the XDA forums come with as little information as possible. They just expect you to know your shit? With that often comes a bit of ambiguity because you’ll probably find different answers for the issues you search for. It can slow things down a bit and involves trial and error. But in the end i always managed to get things happen and i dont have any professional background in tech.
You might want to read up on how easy it is to swap the battery. These phones and with that their batteries are getting old. But in my experience there is for almost every phone a video teardown on youtube.
Biggest battery drainers are the antennas. Without a simcard, no wifi, etc phones can last ages. I use my old phone for a similar usecase as yours. It doesnt get too much use but with that i need to charge it like maybe every 3 weeks or so. Its crazy.
If you want to use the camera you might want read up on if the XZ1 is still a sony phone were the camera quality drops significantly with a customrom. They changed that some years ago. But idk when exactly.
If you want to use it as an offline device mostly for audio anyway(just assuming, idk) maybe just try out the stockrom a bit. It could fullfil your needs already perfectly.
Check out Emulators. That snapdragon 835 should play anything easily up to the Dreamcast and PSP maybe even some lighter PS2 and Gamecube Games.