[Sony Ericsson Xperia Mini, Mini Pro, Xperia Pro, A] Nautilus_:
@Temp_Quack,

Sorry, didn't see your post till now.

Here are my findings so far:

Performance of Xperia Mini with LOS 14.1 wasn't as good as with CM13 ROM, so I downgraded my Xperia Mini to CM13. On CM13 (Androind 6.1) it's really fast and smooth, much better and faster performance compared to Android 4.1.

With LOS 14.1 on my Xperia Mini it started lagging after some time. But the huge advantage was having TWRP recovery (proves to be really useful since you can simply create a backup/image of the system and easily restore the whole image in one step and really fast within recovery itself). With CM13 you only get Cyanogen recovery, so there is no built in backup capability within recovery, but you could make system/data backup with Titanium backup for example. But it's much less convenient compared to TWRP since you cannot make a system image, so in case of restoring a backup you then need to restore one by one app with Titanium backup.

And now to the weird microphone behaviour. This one is REALLY WEIRD. So, here's the thing:

Built-in mic works perfectly if you will be using Xperia Mini on CM13 or LOS 14.1 to make phone calls. Plugged in headphones or headset or bluetooth headphones/headset also work perfectly, no issues with any of them when making phone calls.

BUT if you would like to use any of the (VoIP) apps to make calls, microphone is working ONLY when using WhatsApp, with any other apps which I tested (Skype, Viber, Signal, Messenger Lite,...) microphone DOESN'T WORK at all (tested it also with plugged in headset, with bluetooth headset, with built-in mic... nothing works). I can hear the other side talking, but other side cannot hear me. It's like the mic stays switched off, and only WhatsApp somehow manages to turn it on when initiating a voice call over Whatsapp.

I really have no idea why is that so, and why other apps cannot turn on the microphone.

I then installed some apps that are supposed to be able to reroute / bypass audio signal in the phone, and/or force the microphone audio route (e.g. Lesser Audioswitch and Soundabout), but none of them managed to fix this issue. I would say it's some bug or something missing in CM13 and LOS14.1 which doesn't enable mic (doesn't turn on the microphone) when using VoIP apps. Only Whatsapp manages to trigger the mic (and I also need to mention that sometimes even WhatsApp doesn't manage to turn on the mic, so phone reboot is needed in that case). I really wonder what's the difference between Whatsapp and other apps, I mean how come WhatsApp is the only app that can use/turn on the microphone??

@Temp_Quack: regarding texting, calling (phone calls), wifi and hotspot and bluetooth - they all work fine in my case.

The only thing that's annoying is aforementioned microphone issue in apps, I would really like to get that fixed somehow, but I have no clue what is the root cause of that issue.

Btw, let me know if you'll decide to buy the phone and install e.g. CM13, there might be an issue with Google Play Services that will need to be updated (the stock Google Play Services is outdated and you'll need to update it. Beware not to update it to the latest available version otherwise the phone might be stuck in an endless loop trying to update it without success and then reboots again, then of of the fixes is to clear the cache in recovery which then basically means setting up the phone from scratch again).

You also need to be aware that installing any app will take some time (as far as I remember that's some issue with such ROMs, it's slow when installing apps).

If I think of anything else, will try to make sure to follow up on this post. And if anyone else has any idea how to fix that weird microphone behaviour, please let us know.

Kind regards