Hey! I wrote up a list of Open Source iOS apps on the Privacy Guides community.

I've been slowly trying to become platform agnostic, so I can switch back and forth between OSs without losing function. I'm not 100% there, but I hope this list helps you too if you are looking to go that route.

Copying the relevant bits here.

For iOS:

Fully FOSS:

• Organic Maps - Offline Maps
• Yattee - YouTube Frontend
• BookPlayer - Audiobook Reader
• NetNewsWire - RSS Reader
• Signal - Encrypted Messaging
• Element - Matrix Client
• OrBot - Tor VPN Alternative
• Swiftfin - Jellyfin Client
• VLC - Media Player
• Metapho - Remove EXIF Data
• Privacy Blur - Blurring Photos
• Raivo - 2FA
• Firefox Focus - Web Browser
• Mastodon - Official Mastodon Client
• PixelFed - Official PixelFed Client
• Sync - Reddit App (RIP?)
• Mlem - Lemmy App (currently testing)
• KDE Connect - Airdrop Alternative
• Berty - Encrypted Messenger with Offline Capabilities

FOSS, but with a paid tier:

• KeePassium: Offline Password Manager
• Slide for Reddit - Reddit App (RIP)
• AdGuard - Content Blocker
• Bitwarden - Password Manager
• Joplin - Note App
• Podverse - Podcast App
• NextDNS - DNS Filtering
• Invoice Ninja - Invoicing Software
• SimpleLogin - Email Aliasing
• ProtonMail - Encrypted Email
• ProtonCalendar - Encrypted Calendar
• Proton Drive - Encrypted Cloud Storage (Testflight is Full)
• ProtonVPN - VPN
• Standard Notes - Encrypted Notes
• Notesnook - Encrypted Notes
• Tutanota - Encrypted Email & Calendar

Paid Only, but Open Source:

• Cryptomator - File Encryption
• ente Photos - Encrypted Photo Backup
• Mullvad VPN - VPN
• IVPN - VPN

Don't let perfect be the enemy of good. Start with an android phone from a vendor that runs a very stock ROM. Go with Google for fast updates, teracube or fairphone for long term support and sustainability, or Nokia for a good solid privacy respecting company (not perfect, but pretty good). From there prefer open source play store apps. When you're ready, try F-Droid.

Generally I recommend starting small and escalating

I use a Pixel with GrapheneOS, it has been a perfect OS for me, honestly way less janky than iOS, which I didn't expect. For example, Airpods autoconnect works every single time without fail on Graphene, whereas half the time on iOS it wouldn't connect and id have to go into the menus. GrapheneOS also has additional security and privacy features other Android OS's do not.

linux phones aren't recommended currently for various reasons, they're just pretty unstable and have various security flaws among other issues.

i'd recommend looking into a google pixel and installing GrapheneOS. its open source, and pretty much as good as it gets for privacy and security on a phone. it really is an excellent project.

very easy to set up and install, plus amazing app compatibility, no bloat or garbage, etc. its overall a really good experience, i can't recommend it enough, had 0 issues with it.

either way, despite some of the other replies, i really would not recommend regular OEM android at all. android that comes with most devices out of the box is typically full of proprietary bloatware and spyware and other garbage that you can't remove, and isn't a great experience at all in general.

if you can't get a pixel for GrapheneOS, next best thing is DivestOS, followed by LineageOS.

Just use android don't waste your time with the ubuntu stuff. Graphene/Calyx are also good options if you want a privacy hardened android

I highly recommend Android. Just don't install Google Play Services (use F-droid instead)

I'm just going to mirror a common sentiment. Get an Android phone and just use alternative apps that are open source.

I see you're using Obsidian and I believe that Obsidian is not open source. I'd recommend Logseq as an alternative. I know it does not have as many features as Obsidian and it's in beta, but it's got a really nice community behind it.

Also I always recommend SyncThing everywhere I go. Sync your files directly between your devices. I sync files between my Windows PC, my Synology NAS, my phone, & my Linux laptop. It works like a charm.

Most FOSS Camera apps and photo galleries are not linked to an online photo service for example. So just sync them to your other devices directly instead of using the cloud.

This is a tough problem to solve, there isn’t one solution for everyone.

Many years ago I tried various options such as vanilla Android, LineageOS with gapps, Lineage without gapps and even Replicant. Every option came with pros and cons. If all you need is phone calls, SMS and some simple apps, you could go with any of these options as long as it meets your ideological requirements.

At one time time I had just the pure LineageOS without gapps, and that’s when I realized I was about 10 years late with this project. The world had changed to such an extent that being this strict about FOSS was going to require some pretty hefty sacrifices. When my bank announced that they would eventually phase out the security code papers in favor of their mobile app, it meant this option was a dead end for me.

I couldn’t make the bank app work at all if I didn’t have gapps. If I did, it still refused to work properly, because LineageOS wasn’t the OEM system. After trying a bunch of different workarounds, it was clear: this ship had sailed already. Either I would have to embrace the downsides of current technology or live off the grid without access to money. Doing that would also make my life very inconvenient in a number of other ways.

Online banking was the deal breaker for me, but other apps caused similar problems too. Just about all the modern apps the society expects me to use were either slightly broken or completely unavailable. In many cases, it felt just like using a dumb Nokia 3210 again, with the exception that I had a mobile browser, nice calculator etc.

I wasn’t happy with the situation, nor with the options standing before me. Google is an ad company and users are the product, so obviously Google was the worst option available. Actually, Chinese Android phones are the worst option, but other companies aren’t far behind because of Google.

Apple was a little less bad, but still an unpleasant option. Strangely enough, I became a reluctant iPhone user. Fortunately for me, iOS had finally reached a point where a lot of the basic standard features Android had about 5-10 years ago were finally available on iOS. The decision was far from ideal, but at least I found the right kind of balance between functionality and privacy.

I’m not happy with the result and I can’t recommend you follow in my footsteps, but I highly recommend trying out different options and banging your own head against the brick wall. That’s the only way you can find out how idealistic you really want to be.

Just use a stock Android and de-Google it as much as possible, there are Linux phone ROMs but they are... Well i wouldn't recommend them for normal usage.

Consider this option, see if it suits your current & future needs; https://www.fairphone.com/en/

I’ve played around with Ubuntu touch from ubports foundation on an old pixel 3a. It works ok as a basic daily driver. Depending on the phone model there’s support for waydroid which helps with using android apps.

I use pixel with CalyxOS. I'm pritty happy with it. Its easy to setup but you do need a pixel phone for it to work.