@daniel I ran into this today. Vivaldi was working fine yesterday, and when I came back to my computer today, it had crashed. It wouldn't restart, and doing so manually returned:
➤ ./Vivaldi
[3939:259:0710/064423.849214:ERROR:unexportable_key_mac.mm(348)] Unexportable keys unavailable because keychain-access-group entitlement missing or incorrect. Expected value: 4XF3XNRN6Y.com.vivaldi.Vivaldi.devicetrust
[0710/064424.292970:WARNING:in_range_cast.h(38)] value -634136515 out of range
[0710/064424.303649:WARNING:crash_report_exception_handler.cc(235)] UniversalExceptionRaise: (os/kern) failure (5)
[3958:259:0710/064424.305009:ERROR:shared_memory_switch.cc(244)] Mach rendezvous failed, terminating process (parent died?)
fish: Job 1, './Vivaldi' terminated by signal SIGSEGV (Address boundary error)
Unlike the OP, starting with --disable-extensions did not resolve the issue (which is why I'm writing). The error was slightly different:
➤ ./Vivaldi --disable-extensions
[4465:259:0710/064903.309440:ERROR:unexportable_key_mac.mm(348)] Unexportable keys unavailable because keychain-access-group entitlement missing or incorrect. Expected value: 4XF3XNRN6Y.com.vivaldi.Vivaldi.devicetrust
[0710/064903.835203:WARNING:in_range_cast.h(38)] value -634136515 out of range
[0710/064903.849629:WARNING:crash_report_exception_handler.cc(235)] UniversalExceptionRaise: (os/kern) failure (5)
[4473:14851:0710/064903.857563:ERROR:ssl_client_socket_impl.cc(878)] handshake failed; returned -1, SSL error code 1, net_error -3
[4473:14851:0710/064903.857747:ERROR:ssl_client_socket_impl.cc(878)] handshake failed; returned -1, SSL error code 1, net_error -3
fish: Job 1, './Vivaldi --disable-extensions' terminated by signal SIGSEGV (Address boundary error)
Reinstalling the latest version didn't fix the issue either. The snapshot that you linked to, however, did start correctly. If you want any crash reports, let me know where to find them and where to send them.
I'm running Sonoma 14.5. I'm not aware of any updates that were installed between yesterday and today, although I only upgraded to Sonoma a few days ago. This may be the first time that Vivaldi restarted after the initial boot, so there could have been a minor update over the last few days that created this issue.
I hope this helps, if only to let you know that the snapshot appears to have resolved the issue.