The Offline-First Mobile Setup

Offline-First Emergency and Private Phone Setup

Most of the tracking by companies are done using online connections. So the fastest and easiest way to prevent that is to take your phone into airplane mode, assuming your phone manufacturer didn't put any backdoors in airplane mode function (they probably did, but it is still a valuable feature).

The second use case for going offline-first is being able to use your phone in an emergency when internet services are not available (examples include earthquakes and regular service disruptions an ISP/GSM can have).

Third use case is you are guaranteeing being able to access what is necessary for you in a censorship situation. What you already downloaded can not be deleted remotely in most cases (there was a case Huawei phones deleting photos from peoples gallery apps to censor info related to protests).

What do you need from a phone?

Put your phone away and think what will you miss first if it didn't even existed. Here is a table of what I thought and solutions I found:

What do I need?	Description and Solution	Download Link
Being able to research information	Internet is a valuable research tool. We will download the information before needing it to solve this issue. Download Kiwix in your phone. Then download sources which you think it will be useful. My recommendations are: Wikipedia: Try to download the largest edition of Wikipedia from the list. It will cost a lot of storage. But it worths it since you can use it as a dictionary too. You can download Wiktionary too if you want a separate dictionary. Gutenberg Project: A lot of books, costs 71GB as of writing this. StackOverFlow/StackExchange collection: If you have a computer you need to fix, consider adding them to help you. Arch/Alpine/Gentoo Wiki: Specialized wikis when you need Linux manuals. iFixit: Hardware repair guides. Xkcd: If you are bored you can look at several Xkcd comics and move on. This should cover most needs. You can always download more resources afterwards. If you want to have a faster dictionary app, consider installing Aard2 or QuickDic. They are faster for day to day use. You may want to download Linux Command Library app to look up useful commands faster. There is a dedicated app called WTF for checking abbreviations meaning.
Communication	Phones original reason to exist. Being able to send messages between people. You can use Briar to send messages without needing internet but you will need to convince other people to install it too. Briar can send messages using WiFi (no internet just LAN), Bluetooth and Tor (if you want internet as a fallback). If your city has many people using Briar, the coverage and range will be better. Alternatively you can use Meshtastic devices paired to your phone if there is a volunteer-run MeshTastic antenna near you. If you are not sure about coverage of Briar/Meshtastic or just want a fallback, consider RCS or encrypted SMS. They are not the most secure or private methods. But as long as you have a little signal they will work. DO NOT use SMS without encryption if you want contents of the mesasge to be private. RCS sadly only works on proprietary messengers like Google Messages or Samsung Messages. Encrypted SMS can be used by installing one of these apps (you will need to convinve your contacts to install these apps too): DekuSMS: E2EE for SMS messages. Needs Android 7 or later. Image sharing over SMS (not MMS) Silence: Not updated anymore. Fork of an old Signal version. E2EE SMS. Supports SMS over VoLTE. KryptEY: If any of these apps don't work for you, there is KryptEY. It is an innovative app that can turn any chat app into an E2EE one by auto encypting/decrypting messages and being your secondary keyboard. Switching between keyboards may be exhausting for your contacts so choose if there are no other options.
Navigation	Being able to navigate without doxxing yourself to GSM towers is important. That means your location will be known by one less entity. Also do not trust coverage of your GSM, it can just fail. Use CoMaps (fork of Organic Maps) or OSMAnd+ and download maps for your city and other places you can been to. CoMaps doesn't have Bus support still afaik so I keep both apps installed just in case. If you need a nice UI and bus support, you can try using MapsMe but it is proprietary.
Using LLMs?	If your phone has a powerful CPU and plenty of RAM you can try running LLMs on it. It can be sometimes faster to ask an LLM instead of searching inside archives I have downloaded. The con here being heavy battery usage and risk of hallucination by LLM software.
Translation	Especially between English and your main tongue. You can use Offline Translator. It is not the best but it will do the job. You can still use Google/Yandex Translates offline translation feature but they are proprietary.
Entertainment	Playing games, watching movies etc. I use LibreTorrent to download movies into my phone for later viewing. For games I have RetroArch with several game packs installed for several emulators. You can download other games like DroidFish (Chess Engine) and Luanti too. Try to choose sandbox or board games since they are replayable anytime. You may download news articles that interests you to read. I was using Hacki (HackerNews client) to download tech related news and read when I need to pass time outside. You can use your phone as a ebook reader too. Librera Reader and ReadEra (proprietary) to read my ebooks. It does not count as entertainment but you can download religious texts (Bible, Quran and more) if you want. music
General Real Life Helpers	You can download the multi-purpose Trail Sense app. It has features you will need when outside. Compass, turning paper maps into digital ones with GPS, checking whatever a surface is really flat or not, convert between units, metal detector, mirror mode (so you do not take accidental selfies), save the path you walked, ruler, QR scanner, white noise and more. It has a built-in survival guide too for emergencies. The other useful app is Survival Manual. The name explains all.
Memory Helpers	A note taking app and a password manager is very helpful outside. For noting I use QuillPad. For passwords I use KeepassDX. You can prefer Bitwarden for easier sync. They should be able to run offline and sync only when you connect to a network.
Wallet App	You can use OSS card wallet to remember your card details even if you don't have them outside.
NFC/IR stuff	Niche stuff but sometimes helpful. You can create a copy of your public transport card if you ever lose it. About IR, I rarely use it to control air conditioners when nobody is able to find the remote for some reason.
File transfer	Consider installing LocalSend to you and your friends phones. So you can transfer files easily if you are on same Wi-Fi network (you can always use your hotspot too).