This “defaultTokenProvider does not exist” error turned out to be a web server issue. OpenBSD’s httpd is chroot’d to /var/www by default, so /etc/ssl/openssl.cnf was not accessible by the web server user (www in this case). Simply copying the file to /var/www/etc/ssl fixed the issue.
Had also been having a database issue on another thread, which was caused by a sneaky issue with OpenBSD’s php-pdo_pgsql package. At some point I had set root’s umask to 027. Then, during an update, some of the files in this package that are created on-the-fly took on these restricted permissions, and the www user could no longer access a small set of the php pgsql module files. (I forget which files off hand…) Update these permissions, removed that umask, and all is well with the world again.