Blackberry contacts app no underline in username for server

Hi all,
yesterday I got my KEYone and transfered "all" data via content transfer app from OS10 to Android. This did not work out ok, but that would be something different. One part was the transfer off accounts, I had email accounts and native calDAV and cardDAV accounts configured which were not transfered. Not a big deal normally, but when I now try to setup these accounts for example in Blackberry contacts app, I can not connect to the server, it is a Synology NAS system, reachable by Web, Thunderbird and another OS10 device.
1st is that the app tells me the server is not reachable, and when I try different URLs the one containing the "USERNAME" should be "joerg_nc" but the underscore _ is not available.
Do I really need to use DavDroid or an other tool to get the job done?
rgds - Jörg

Hi,
just got my keyone and was doing setup this evening and i had the same problem.
No underscore allowed in the server settings, and my nextcloud username includes a "_" so no native carddav setup for me.
DavDroid works fine but for some reason no contacts show up this way in the nativ bb contacts app, but using search or another app for the contacts lists them just fine.

have to live with that for the moment....