While booted into Recovery Mode, try running Disk Utility First Aid on the physical SSD, then on the hidden Container. Within Disk Utility you will need to click "View" and select "Show All Devices" before the physical SSD & hidden Containers appear on the left pane of Disk Utility. I would only run First Aid on the main OS Container (one with "Macintosh HD"). I'm not sure I would run First Aid on the other two Containers since if something happens to them, then you are screwed if you don't have a backup since the only way to recover at that point is by a DFU firmware Restore which resets the internal SSD destroying all data on it. If you have tried everything non-destructive, then you could try running First Aid on the other two hidden system Containers since at that point you really have nothing to lose.
You can try reinstalling macOS over top of itself.
You can try a DFU firmware Revive which resets the security enclave and system firmware.
You can also try clearing the NVRAM while booted into Recovery Mode. Launch the Terminal app from the Utilities menu on the menubar and issue the following command (safe for M-series Macs):
nvram -c
Reboot the computer to see what happens.
If none of this works, then you will need to wipe the system by performing a DFU firmware Restore which will destroy all data on the internal SSD.
I doubt a professional data recovery service will be able to recover any data from a locked encrypted SSD, but you can always ask.
You can also have Apple or an Apple Authorized Service Provider examine the laptop to see if there is any way to access the data on the internal SSD (an AASP will likely be better here since Apple really doesn't do data recovery, but some AASPs may).
I hope you have backups since there is very little chance of recovering the data now if you have no valid users on the system to authenticate against to unlock the encrypted internal SSD.
People should always have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data. There are a lot more new ways to permanently lose access to the data on the internal SSD of the recent Macs due to all the hardware, software, and security changes.
