FOSS app which I use -

• Jerboa: Lemmy Client
• Megalodon: Mastodon Client
• RiMusic: YT Music Client
• Drodify: Material You F-Droid Alternative
• Libretube: YouTube Client
• FluffyChat: Matrix Client
• Monocles Chat: XMPP Client
• KISS Launcher: Fast and Clean App Launcher
• Cherrygram: Telegram Client
• Revolution IRC: IRC Client
• SD Maid SE: System Storage and app cache cleaner.
• SuperFreeze: Help in Force Stoping the app
• Next Player: Material You Video Player
• Diohub: Github Client
• Gitnex: Codeberg(ForjeGo/Gitea) Client
• Native Alpha: Webapp Manager - Help in creatimg Webapp
• APK Kit: APK Exporter + Give detail of Everyapp
• Material Files: File Manager
• Kiwi Browser: A better Chromium browser which Chrome Extension and Inspect Element Features AKA Dev Tools.
• Fossify Gallery: Gallery App
• Atomic: A Periodic Table App
• OpenCalc: Material You Calculator
• Proton Mail: proton.me only support its own client :(
• Psiphon: Open Source VPN(Only Client)
• Arcticons: A Line Icon Pack
• MJ PDF: A PDF viewer.
• Simple Keyboard: Best Minimal Keyboard.
• Mauth: A 2FA app
• DNS quick Tile: Add a system DNS quick to turn on or off from notification bar.
• also de-googled my device

Closed Source app which I use :( -

1.Modded

• Whatsapp Beta Mod - Privacy Features (Use because of School)
• MyInsta: Modded Instagram (Use because of friends)
• Duolingo: Removed Ads and Tracker(Use because that Green Owl have My family)
• Mimo: A code learning app - Removed Tracker and Ads (Use for fun)

2. Non-Modded

• Mobilisim: Where I got my All Mods
• ApkTool M: Android Apk Editor (Installed it when I really need it like changing package name of an app or removing a alarming permission from an app) - Give me suggestion for this app if you know

Suggestion For OP

OP You should use Florisboard beta it's good and also Obsidian is not open source.