I am not an expert on security and I don’t know how to setup ddns, but I simply use Tailscale VPN to access my RPi4 homeserver running Umbrel from outside of my home, I simply installed Tailscale in my Umbrel and in my phone, and when I want to access from my phone Immich, Nextcloud or any other app running on my Umbrel. I simply enable the Tailscale VPN. Maybe it has some limitations, but is the simpler way I found, and based on what I read, it is more secure than exposing a port in the router, but not sure.

I don’t know why you say that bitcoin is mostly used to scam people and to purchase illegal goods. I agree that maybe a small fraction of people is using it as a currency. But, in my case, most of the people I know who have bitcoin, just have it as a store of value. Maybe I am lucky and know a lot of those “responsible heroin users” who understand that there will be only 21 million bitcoins, so what makes it valuable is its scarcity, and as long as central banks keep printing money out of thin air, bitcoin demand will grow, at least among those who understand it.

I don’t want to say crypto in general, but Bitcoin in particular was born after the 2008 crisis, as a decentrized form of money, meaning storing value against the inflationary fiat money that the goverments can print in a centralized manner, destroying all your savings. I think any technology that empowers decentralization is positive. Same as fediverse. And in the case of bitcoin, having a decentrized money it’s a really positive tool for freedom to avoid centralizing the power in the governments. But I am curious on knowing why you say that there is no positive uses.

Umbrel OS

I use Logseq in my PC and my phone and I unse Syncthing to sync the notes accross my devices.