Recover your data from a backup you made before the laptop failed. You should always have multiple copies of any important data stored on external media.
There are only four major components in a 2019 MBPro -- Display, Top Case Assembly (Keyboard, Trackpad, Touchbar, Speakers, Battery), Logic Board (CPU, GPU, Memory, SSD, WiFi), and the I/O Boards (aka USB-C connectors). Even so it can sometimes be a bit difficult to narrow down the issue unless the tech has access to known good parts for testing & troubleshooting. Otherwise it is just an educated guess on which part to try to replace first. These USB-C Macs are not easy to diagnosis as they have a lot of unusual behaviors not seen on any other computer or older Mac.
Now here is the real tricky part. A 2019 Mac uses a T2 security chip which automatically encrypts the data on the SSD using hardware encryption. The T2 security chip has the encryption keys so if anything happens to the T2 security chip, then there is no way to ever recover any data from the hardware encrypted SSD. In fact some normal troubleshooting procedures involve "Restoring" the T2 firmware which destroys all stored information in the T2 chip thereby permanently losing access to any data on the hardware encrypted SSD. Plus a simple OS update may even potentially corrupt the T2 chip causing you to lose access to the encrypted data.
If the Logic Board has failed, then it is hard to say whether an expensive professional data recovery service such as Drive Savers or Ontrack will even be able to access any data on the SSD. If the Logic Board is bad, then most likely someone will need to repair the Logic Board just enough so that both the T2 security chip and the SSD function to access the data.
It is up to Apple or the AASP to determine which part or parts are bad. An AASP (not sure about Apple) does have access to a service utility to attempt to retrieve data from the SSD, but like I mentioned the computer must function enough to be put into DFU Mode. If the Logic Board is bad, then you will need to make decision on whether to have a professional data recvoery service attempt data recovery before the shop replaces the Logic Board and completing the repair.
You should always have frequent and regular backups of your computer and any external media which contains important and unique data. The more important the data the more copies of the data you should have. Also if you don't have another Mac, then you need to make sure your backup solution allows you to access the data on the backup drive. Plan ahead the best you can before disaster strikes to minimize data loss.
