How would one go building a router? I was planning on getting wired networks for a NAS build but most providers seem to ship their own router which probably is a nightmare for privacy, can I just pay for internet and use whatever router I want?
If you have USB debugging on then yes. If not try to see if you can mirror display with USB and a TV/monitor. If that doesn't work a USB mouse will have to do if you know that layout of your phone. A keyboard could also work for the pin. I always suggest leaving USB debugging enabled and paired to your computer so in such cases you could just do
adb pull /storage/emulated/0(or another number if you have different users or work profile /path/to/desired/location
This way you'll pull all the data from everywhere and delete what you don't need. With USB debugging enabled you could also use SCRCPY, it's a neat tool that'll mirror your screen and you can control the phone with computer mouse and keyboard.
If you do want to try and enable it'll be in Developer options/settings, if you have them enabled if you don't you gotta press on Build Number in your about phone section in settings.
Liveusb sistems do get stored in RAM since it's so much faster and reliable. Also I'm pretty sure most liveusb are read-only so it's Hardee to modify data. Manjaro must be loading small parts into Ram, or you didn't had enough ram, so when you took it out it only had the data on RAM which wasn't enough for it to process any command
Nvme would be much faster, I personally use the one from ugreen which is ~30€ plus a nvme with 2-3gb read/write speed for around 100€. You can find 1tb for 100€. I don't know any good USB sticks that can do that much
How would one go building a router? I was planning on getting wired networks for a NAS build but most providers seem to ship their own router which probably is a nightmare for privacy, can I just pay for internet and use whatever router I want?