Softether or alternative vpn for nonpublic ip

The problem:

I have turris omnia set-up with nas and nextcloud. I would like to access the content of the nas from mobile phone android when i am away over 4g. The thing is my ISP does not give me public ip. The router has local ip assigned by the ISP and is behind NAT i dont control.

I have read somewhere that softether vpn should be able to work behind NAT, and it seems here is a tutorial for installation of softether. I am also not clear if it means all my traffic will go through some relay in internet where someone else can acces it. But before i spent time figuring out how to set up containers on my turris omnia, i would like to ask if this set up will work or if there is some other better solution…