linuxmemes

It's hard to say if it will work for you. For some people it does and for others it doesn't. It's just something you would have to see for yourself and it might require some time to set everything up the way you want it. It's a device that requires tinkering. Voyager seems to have a web version and so does FluffyChat. I use Nheko Matrix client (available in Mobian/Debian repo) - it's a native app that works pretty well. I don't know about the other apps, but in general you can run Android apps through Waydroid. Maybe those would work too.

There are no push notifications, so if you want the phone to suspend and still receive Matrix notifications, you would have to setup a script that will wake the phone up periodically.

Pictures (taking and viewing, maybe nextcloud upload but that could be done by a script as well)

This works on the original PinePhone, but the camera itself is pretty bad. PinePhone Pro has a decent one, but I'm not sure what the current state of that is. My understanding is that it works, but the pictures might not look that great. I think it's only one guy working on the camera app and he is currently working on a new version: https://blog.brixit.nl/fixing-the-megapixels-sensor-linearization/. For syncing files with a desktop I use SyncThing, but Nextcloud should probably work too. For sending just a few specific files from time to time you could use KDE Connect or even just SSH.

Web browser

That works. I use Firefox. PinePhone doesn't have a lot of RAM, though, so you won't be able to have a lot of tabs open at once.

Music

Definitely works. I use Lollypop app (available in Mobian/Debian), which works well on a mobile screen. The phone has a headphone jack if you need it. The speaker isn't very good.

Calls

This works, but audio quality during phone calls isn't always good. There also seem to be some modem issues on PinePhone Pro: https://zerwuerfnis.org/daily-driving-the-pinephone-pro. I think it's currently recommended to install the free modem firmware and I'm not sure if the author was using that (the phone doesn't come with it installed).

I'm not sure if MMS works (SMS does), since I don't use that. Support for emergency broadcasts is now being added to Phosh: https://phosh.mobi/posts/cellbroadcast/

You should also know that the battery life isn't very good. So if you use the phone a lot, you might need either an extended battery case or spare batteries (the battery is replaceable) or the keyboard addon.

Edit: I have a stupid idea! I fondly remember my blackberry from back in the day. Obviously its not for the mainstream but pinephone isnt either. Wouldnt a step back to a blackberry design be pretty awesome for us nerds? :)

I don't know which one you mean, but I would love to have a slider keyboard! Technically you could make one and I've been wondering how hard that would be. PinePhone has some pins on the back that you could use - one of them is i2c. The keyboard addon from Pine64 uses them (they have other addons too). It's probably a lot of work to make something like that, though.