Thanks for the suggestions to both of you. In the meantime I modified the server config to also allow older protocols and found out that, for OSMC/Vero4K, mounting and autofs works up to SMBv3.02. Interestingly (from the other topic I already mentioned above) it seems to be working up to the latest version SMBv3.11 for OSMC/Pi. Just out of curiosity, do you know the reason for that?
Back to the original issue: At the evening I will check if autofs solves this.
Chris