Anyway: What can the iPhone 5s on iOS 12 still do without jailbreaking and what it can't do? I'll make a list of various apps I've tested and whether or not they work out of the box or not on the latest iOS you can run on the 5s: (Alternatively if some of these don't work for you on iOS 12: you need a newer iOS device install the desired apps on the account you wanna use so that it's registered under your account. Yes, some apps will now allow you to install older versions otherwise.)
Youtube - App does not work however it sluggishly works through Safari.
Google Maps - App works, takes a while to load initially but once everything is done loading it should be a smooth experience.
Discord - App works, old version with the older UI, very slow, takes a while to do anything but it works.
Netflix - Doesn't even install. (however it may be a matter of it requiring iOS 17.0 and I don't own a device able of running that version of iOS)
Spotify - Allows an install but refuses to log you in through the app and the browser asks you to install the app due to the browser not being supported.
Apple Music - Not subscribed so I can't test how functional it is but the iTunes Match sync works since I can listen to my iTunes library including non-iTunes Store mp3 files which makes me feel somewhat confident it might work.
Soundcloud - App not supported but it works through Safari, albeit incredibly slowly. (requires iOS 16.4 and I don't have a device able to run that version)
Bluesky - The latest supported version is so old it predates the butterfly logo, instead having the sky icon. Unsurprisingly it asks for an update. On Safari, Firefox, Opera and even DuckDuckGo Browser it stays stuck on the butterfly logo.
Twitter - No chance through the app but Safari allows you to log in and use Twitter if that's really what you want.
Reddit - App installs but stays stuck at a blank page, Safari allows you to check Reddit but only one letter per row at a time therefore not what I'd describe as usable.
TikTok - App does install but everything is so slow that it's practically unusable.
Telegram - App works fine
If you also have an iPhone 5s and you desire to jailbreak it here's the guide I used: https://ios.cfw.guide/
Keep in mind this is done at your own risk and I am not responsible for any damages or misuse nor am I affiliated with anyone behind the guides.
After a lot of tinkering I was able to trick YouTube into thinking it's the latest version which made it work. The UI is broken here and there but by all means everything works as you'd expect! It may be prone to crashing but in that case clearing cache will bring it back to an operational state.
Spotify works too using the same trick but only lets you log in via email. Otherwise it's perfect.
Reddit was a no-go, Bluesky I wasn't quite lucky at all, likely due to how early that version was and when it comes to apps that don't allow you to install old versions any longer your only option is sideloading. When it comes to Bluesky I even did the YouTube and Spotify trick over onto Opera in hopes it'd do something and nope. No sign of life.
Obviously to me this isn't all out daily-driver level capable especially due to Bluesky not working in any capacity. As much as some people might scowl at me the 1st Gen SE is still daily-driver worthy to me. The 5s is good if you just mainly want a phone that can do a little more than the absolute bare basics though.
Anyway I am still learning about this so to my knowledge I could be doing this all wrong so advice/constructive criticism is welcome. I still feel proud of myself since I've learnt quite a bit about Apple devices in recent times despite never owning one until last year around this time. I still am team Android but I've gained a newfound respect of sorts too at least for classic iPhones and older Apple devices as a whole.