Error with enable_previews = false at config.php

Hi there,

Fresh installation on Ubuntu 22.04, php 8.3 in FastCGI mode, latest Nextcloud 31.02, LibreSign 11.0.4. (no upgrade history)

All dependencies installed, all green-success in NextCloud LibreSign Configuration check window.

OpenSSL engine case: entire workflow works, except when pdf is signed, 'explode(): Argument #2 ($string) must be of type string, null given' message is returned in the upper right corner.

Nevertheless, pdf is created, stamp, qr and certificate are all attached to it.
However - signature validation functionality does not work (same 'explode(): Argument #2 ($string) must be of type string, null given' is returned).

Tried 'I will not use root certificate' and 'CFSSL' even with less success - 'Failure on generate certificate' is returned when attempt to sign.

Re-installed LibreSign multiple times from NextCloud UI.
Re-installed LibreSign with occ:
occ libresign:uninstall --all
occ files:scan-app-data libresign
occ libresign:install --all

Re-issued certificate with different parameters multiple times.
Log file does not give any additional hints (same as above).

Would be good to have at least OpenSSL method working.

Looks like this error was mentioned (on the web) at least twice previously, but outcome is unclear.

Thank you.

Start with config.php and reproduce the OpenSSL signing and signature-validation workflows on the stated Ubuntu, PHP, Nextcloud, and LibreSign versions. Check the occ installation commands and the reported explode() null error, then verify that signing completes without the error and that signature validation works.