Phone suddenly shut down and won't boot up

My phone (Xiaomi Redmi Note 10, 2 years usage, the warranty just passed) suddenly shut down at 50% battery at normal usage when I clicked an app to open it and it will not boot up. I want to fix it myself due to privacy reasons, as I don't trust payed services and have experience in opening phones, but only to replace the screens. I tried to turn it on on safe mode - unsuccessfully. I tried to charge it but it didn't even pop the animation of charging. Nonetheless I left it for couple hours to charge and tried again - still not booting up. The USB connector is clean, dust-free and not loose. I tried different chargers. It is not detected by the computer when plugged in (checked in the Device Manager, Windows). I also called the phone from another phone to check if it's the screen's issue - I got "user out of service" message. I tried to troubleshoot the connector and it was a surprise to me: I own a MakerHawk UM34C USB 3.0 tester and tried it on my working phone - readings were reasonable, approx. 13W of charging power. I tried it on bunch of other devices, with correct readings. I also tested a device with physical on/off switch and the device showed voltage of 5V when turned off (charger voltage) and voltage + amperage when turned on (with propper readings). **So when I plugged it in the phone and if the connector were bad then I should have the same reading as in the device with off switch. But what I got was device (tester) restarting constantly without even showing me the data, as if the connection was ok but the phone "intentionally" disconnected it repeatedly.** This means that the phone recognises the charger and disconnects it immediately. What does it imply? Is it the software issue? I tried to open it like on the vid, using same tools but the glue seems to be too strong and it won't open so I can't check the battery itself without damaging the phone: https://www.youtube.com/watch?v=PhC37fp4o7Y **How should I troubleshoot the issue?** These threads provided no help: https://android.stackexchange.com/questions/171472/galaxy-s4-not-booting-up https://android.stackexchange.com/questions/247451/poco-m3-pro-5g-not-booting-up-after-unexpected-shutdown-it-does-not-charge-as-w