Try booting into Safe Mode.
Did you try Internet Recovery Mode using Command + Option + R?
Did you modify the laptop's security settings using Startup Security Utility to allow booting from USB prior to this issue? If not, then you cannot do so now if you cannot access recovery mode.
If you have access to another Mac currently running macOS 26.x Tahoe or macOS 15.7.3+ Sequoia, then you can try a DFU Firmware Revive to reset the T2 security chip & system firmware (instructions must be followed exactly & may take multiple attempts to get a Mac into DFU Mode). Maybe it will allow you to access Recovery Mode (Command + R) or Internet Recovery Mode (Command + Option + R).
If you have a good backup of your data, then you can use DFU Firmware Restore to reset the T2 security chip, system firmware, and internal SSD which will destroy all data on the internal SSD. You will then need to use Internet Recovery Mode to reinstall macOS onto the empty internal SSD.
If you don't have a good backup, then you can try putting the "broken" laptop into Target Disk Mode to see if you can access the data from another Mac running macOS 10.13+, but you will need to connect the two Macs using a Thunderbolt cable. Or you can contact a professional data recovery service to see if they can recover any data from the internal SSD.
