I'm sure those who are intelligent enough to read this blog will be using an Android phone (or no phone, that's fine).
However many of these use much proprietary software that force you to stay inside of a specific ecosystem
So in this entry, I'm going to recommend some cool software to make your phone more freedom and privacy respecting because the modern world is scary!
LineageOS (forked from CyanogenMod) is the universally recongnised custom Android ROM, that most will install on their modded devices If your device can't be flashed then you'll have to continue with your Google-OEM-Android but maybe you shuold consider getting another phone that can be flashed Other OSes include:
F-Droid is your preferred source of applications for Android, instead of forcing tons of useless dependencies, F-Droid allows for the developer to push their raw build to either the f-Droid repository or their own repository. The offical F-Droid repository doesn't offer closed-source software. There are other clients for F-Droid including F-Droid Classic, Foxy Droid and G-Droid. Avoid the Google Play store, Samsung Galaxy Apps store and Huawei AppGallery. If you require Gooogle Play services, microG services are an open-source replacement.
Personally, Firefox has a bad mobile experience. I much prefer Bromite, a Ungoogled Chromium fork that respects privacy, sends no telemetry and hides all personally identifying information. The Bromite Project also offers Android SystemView replacements and Ungoogled Chromium without Bromite patches. For Gemini, I use and recommend Ariane. Avoid Google Chrome, Samsung Internet, Microsoft Edge, Amazon Silk etc.
F-Droid is plentiful in note taking apps as these are simple. I tried Standard Notes but was disappointed with features being behind a paywall so switched to neutriNote CE, which while ugly and simple, is powerful software. Avoid: Evernote, Samsung Notes, Standard Notes.
If you are going through this guide, you most likely want to cut down on social media usage too However I know this may not be possible so here are some clients for access soscial media without reliance to Google services. NewPipe: YouTube, RedReader: Reddit, Barinsta: Instagram, Clover: 4chan, yaxim: XMPP, Yaaic: IRC, AntennaPod: podcasts, Fritter: Twitter
Use KeePassDX. Avoid LastPass, Bitwarden, Dashlane etc.
The idea of VPNs for privacy is stupid and shouldn't be used for that reason. Tor can be used to anonymise you properly.
These are just other stuff that doesn't fit anywhere else. SpotiFlyer: downloading music, KOReader: eBooks, Kiwix: Offline Wiki reader, Port Authority: scan ports in your network, useful for hobbyists, enthusiasts, network admins and the paranoid.
 Both privacy-focused ROMs exclusive to Google Pixel (why de-Google but still buy a Google device?)
 The GNU Project's favourite Android version, fully open-source, no non-free components for booting, small list of supported devices and very hit and miss, YMMV.
 As the name implies, these are based on GNU/Linux and henceforth are not Android. This article won't cover them as I have never tried them and they are super niche, YMMV.
 Android Open Source Project, aka Build-Your-Own-Android, compilation requires GNU/Linux, at least 4 cores and 32GB of RAM.
 I believe there is a microG competitor called QuackGapps or QuackTheGapps.
 Specifically Ariane 2.4.0, the latest version in the F-Droid repository, I tried Ariane 4 and saw the UI was more obtuse and they had added unneeded animations to the page, sadly there is no good alternative to Ariane so deal with the soyware or use deedum.