@rfc2822, may application was moved back to the old server.
now all cipherspecs are available again, nothing was changed on the old server !
Only my Nextcloud was first migrated to a newer server, there Nextcloud was updated from 13.0.7 to 14.0.4, the problems occurred.
now the Nextcloud has been moved back to the old server.
But now it is still Nextcloud 14.0.4 !
Could it be that it’s not the cipherspecs but the old DavDroid has a problem with Nextcloud 14.0.4?