I was late to the party in a previous thread but I have some bangers here. Some may require a license purchase for all features.

-Revanced for YouTube/YouTube Music. Revanced-Extended too. Same thing, but extended is a fork with more features. Sooo many great features in this like removing all ads, sponsorblock, return YouTube dislikes, changing UI, referring to old better UI. So many, check the sub r/revancedapp , Github

-Relay for Reddit Pro Just my favourite Reddit app Play store link

-GoodLock on Samsung phones, especially my Fold. All the modules for it. Lots to choose from Galaxy store link. There are plenty of videos on YouTube for this showcasing the features.

-Solid explorer. My favourite file manager. You can connect cloud services to it too. My favourite for many years Play store link

-KWGT for custom widgets. You can download packs or create your own Play store link

-Nova Launcher, I used it for many many years, but now it's not so great with my fold. But I'll link it anyway, the best launcher if you're willing to tweak it to your likings. Samsungs good lock gives me most of what I need now with the OneUp and Theme Park modules for it. But here's nova, still an amazing option for a standard decide. play store link

-PopcornTime for movies and TV. I'm not sure if I can link it here, but I'll link the sub, check it's sidebar for links r/popcorntimeapp

-Seal for downloading videos, from most services. It intergrates with YouTube Revanced and ads a download button. FDroid link

-Instander, it's a modified Instagram app. Lots of cool features, downloading, ghost mode, upload quality improvements, and more. Link to devs website

-Parcels, best parcel tracking app. Pro features cost £3.49 a year I believe to get push notifications. Can add tracking from all providers, auto adding from select commerce sites too. Play Store Link

-Notify for Mi Band, a must have if you have a mi band. This app is soooooo much better than the stock one. The customisation is amazing. Play Store Link

-Flud, my favourite and best torrent client. Play Store Link

-Auto Notification, useful for permanently blocking persistent notifications such as do not disturb. Can also add a mark as read button to Gmail notifications and more. That's my use case though. Play store link

-AdAway, but only if your rooted https://adaway.org/

-Adguard is great, I just use the private DNS settings to achieve adblock though. The DNS is dns.adguard.com

-Firefox, my favourite browser these days. I ditched chrome a long time ago. Paired with the Ghostry add-on and Dark Reader for full dark mode on all web pages it's amazing. Firefox, Ghostery Link, Dark Reader Link

-Galaxy Max Hz, for Galaxy decides with high refresh rate displays. Can fine tune settings more. Must have to get the best experience and battery life. XDA Developers Link

-XManager, for installing a modded Spotify, simple to use and effective https://www.xmanagerapp.com/

There's probably more I'm missing since I just recently got a new phone. I'll update as I find them