They don't offer webdav or rsync...well yes, they offer but you have to pay 😉
Swisscom is selling the webdav and other services for the storebox product...
So, is not a "technical" problem...is a "business" problem 😉
What I did and what I recomend to everybody.
I changed the operator... same speed, same or better performances, for... 20 CHF less per month.
I took a storage box in hetzner: https://www.hetzner.com/storage/storage-box/bx30 for... around 10CHF per month with 1 TB with ALL THE STANDARD protocols availables plus a lot of nice features :