[Solved] Setting up global access to Home Assistant on Raspberry Pi via VPN with Aero2

Hello forumers,
I am asking for some advice and to clear up my doubts. I have Home Assistant running on my Raspberry and would like to access it globally if only from my phone. Locally everything connects correctly but I keep having problems with global access. My provider is aero2 so I guess access is blocked but I don't know because they haven't given me an answer yet, the SIM card is in the modem and the modem is in the router. However, I have come across advice which, as far as I understand it, still directs me to set up a VPN server to redirect connections there. Is there any chance here to marry these devices to each other? The external IP address I think I have is fixed but I am not sure. I've flipped through too much information on this topic today and it's all getting confused....

Looks like your provider is blocking outside access or at your home you have NAT and no port forwarding.
Read about VPN https://www.zerotier.com/ has good integration with Home Assistant.
It creates its own subnet with private IPs that you can connect to without any problem.

Hello, just after describing this problem here I came across just such a solution and theoretically I have already configured it however I had no external access, now I have had a bit of a break, if I can figure it out I will describe what and how.

The problem was solved by adding a VPN Zerotier . I used these guides during configuration:
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