Hardware far outlasts software in the smartphone world, due to aggressive chronic designed obsolescence by market abusing monopolies. So I will never buy a new smartphone - don’t want to feed those scumbags. I am however willing to buy used smartphones on the 2nd-hand market if they can be liberated. Of course it’s still only marginally BifL even if you don’t have demanding needs.
Has anyone gone down this path? My temptation is to find a phone that is simultaneously supported by 2 or 3 different FOSS OS projects. So if it falls out of maintence on one platform it’s not the end. The Postmarket OS (pmOS) page has a full list and a short list. The short list apparently covers devices that are actively maintained and up to date, which are also listed here. Then phones on that shortlist can be cross-referenced with the LineageOS list or the Sailfish list, which seems to be exclusively Sony¹.
So many FOSS phone platforms seem to come and go I’ve not kept up on it. What others are worth considering? It looks like the Replicant device list hasn’t changed much.
(update) Graphene OS has a list of supported devices
(and it appears they don’t maintain old devices)
Pixel 9 Pro Fold (comet)
Pixel 9 Pro XL (komodo)
Pixel 9 Pro (caiman)
Pixel 9 (tokay)
Pixel 8a (akita)
Pixel 8 Pro (husky)
Pixel 8 (shiba)
Pixel Fold (felix)
Pixel Tablet (tangorpro)
Pixel 7a (lynx)
Pixel 7 Pro (cheetah)
Pixel 7 (panther)
Pixel 6a (bluejay)
Pixel 6 Pro (raven)
Pixel 6 (oriole)
So Graphene’s mission is a bit orthoganol to the mission of Postmarket OS. Perhaps it makes sense for some people to get a Graphene-compatible device then hope they can switch to pmOS when it gets dropped. But I guess that’s not much of a budget plan. Pixel 6+ are likely not going to be dirt cheap on the 2nd-hand market.
¹ Caution about Sony: they are an ALEC member who supports hard-right politics. They were also caught using GNU software in their DRM shit which violated FOSS licensing in a component designed to oppress. Obviously buying a new Sony thing is unethical. But perhaps a 2nd-hand one is fine. It’s still dicey though because the 2nd-hand market still feeds the 1st-hand market and rewards the original consumer. Sometimes it’s clear you’re not buying from an original owner, like someone on the street with a box of 100+ phones.
Essential: navigation (and update maps over Tor), VOIP over VPN, render locally stored PDFs (pushed over adb).
Non-essential: XMPP (snikket), notes, calculator, take photos, scan QR codes, play from local music library
GPS navigation is heavy because calculating a fix from GPS satellites is always CPU intensive. This means (on old phones) the always-on screen coupled with CPU load while navigating drains the battery quick, which is a compounding problem because old devices are less efficient. On top of that, the CPU heat degrades the battery and charging performance when it is most needed. I would rather not strap a power bank to my arm. In principle I should navigate with two devices:
That would also mean when I stop for food or something I could charge both devices at the same time and they would each drain slower when used. Bluetooth uses much less energy than GPS. This approach is inspired by my PalmOS days, when a palm pilot had no GPS and there were dedicated separate tiny GPS→bluetooth devices. The tech exists but I think the GPS server app is either absent from f-droid or it requires a newer device (I forgot which).
GPS decoding is less computationally difficult than you seem to think, and in any case, in phones it's done by a hardware module. The Garmin Geko handheld GPS was made in 2003 and ran on two AAA cells for 12 hours or something like that. Today's GPS's fit inside wristwatches and use even less power. It's just not that big a deal. The cpu load of mapping applications on phones is dealing with the maps, computing driving directions, etc.
I wouldn't worry about map updates by internet. The roads don't change that often. You can update from a USB-connected computer once a year or so and be fine.
The other stuff doesn't sound too bad, though idk why you want a phone for the purpose. If the GPS is for road navigation you can get an old dedicated unit that runs on 12 volts do you don't have to mess with batteries. Those were nicer than phones in some ways. I still have a couple of them kicking around.
I can’t see a wristwatch defying physics. It likely has to calculate your position fewer times per unit time, thus gets an updated fix less frequently than a phone. Which may be good enough when on foot. Otherwise it would suck the battery dry if it works too hard for a frequent high res fix. (edit: see item 4 on this page Looks like you get one calculation per second which is possibly a bit too infrequent for cycling unless the app is good at using other sensors to estimate intermediate positions)
When I said CPU load, I should have spoke more generically because indeed a dedicated chip is used. But that chip still needs energy. A dedicated GPS device would indeed help my situation, whether it’s a phone or otherwise. Getting an old dedicated satnav device isn’t a bad idea. The maps on those are far from useable but I recall some Garmins and Tomtoms had bluetooth and I think sending NMEA info is common. That might actually be a good way to repurpose an old obsolete dedicated satnav device -- or phone that can be configured as such. There is an opentom project to put FOSS on a Tomtom.
I just meant the amount of computation required of a gps receiver isn't huge by today's standards. Remember that gps was designed in the 1970s for use with the technology of that era. Today's stuff is 1000s of times faster.