You may try to use this RPM : https://git.sailfishos.org/mer-core/buteo-sync-plugin-caldav/merge_requests/73#note_60319
- To install it,
devel-su pkcon install-local buteo-sync-plugin-caldav-0.1.71-1.armv7hl.rpm - To revert to the official 3.4.0 version,
devel-su pkcon install buteo-sync-plugin-caldav
It is not exactly based on the 3.4.0 release, but on the HEAD of the master branch plus the patch proposed in the mentioned merge request.