Calendar, WiFi sync with thunnderbird without Box or server?

Apps
1

HI
Is there any “calendar” app that is able to synchronize it with thunderbird in direct wifi, without help of BOX or server?
tks

2

Maybe DecSync CC | F-Droid - Free and Open Source Android App Repository ?

3

If you have a mail server and no caldav server: At least in past thunderbird supported sharing calendar entries by mail by inviting someone.