These shoes were so expensive when they came out. I don’t see why it’s such a big deal to keep supporting the app. It doesn’t mean they need to dedicate a dev team. ...
Don't they 100% have to dedicate development time to updating this thing? I'm not a big computer dork, but I'm pretty sure applications don't just magically work with all device updates.
Which Unihertz phone? People have reported successfully running LineageOS on Jelly Star and Jelly 2. The builds they're using were updated within the past month, and are maintained by a recognized contributor.
Warning: On every device I've installed LineageOS (6 of them so far), I've accidentally soft-bricked it and had to restore it before doing it correctly. So back everything up that you don't want to lose.
Probably using TWRP. Note that the backup is only good for before you switch to LineageOS. After you're on LineageOS, you'll need to make a new backup.
We were using a fork we customuzed of an open source package (we will merge our additions but the team wants us to wait until they're done with a major revision). At some point another upstream package made a fundamental change that broke everything. So we learned the hard way to have upper bounds on all required package version numbers lol. That was such a pain to investigate.
It shouldn't take any development time, but the app stores are all run on over-caffeinated ferret logic, so yeah, they do need to have someone update.
Keeping things updated is like a week of work for one junior developer every few years. A small team could do it for a large company's apps in perpetuity. But under the ideology of capitalist software management, keeping such a team around is functionally impossible. (They would have idle time, some manager would see that and give them extra work, then when the app updating job picked back up, that manager would convince everyone that the other work they were doing is more important than updating apps.)