Look:
I think you search that: https://developer.hashicorp.com/vault/tutorials/pki/pki-engine
I used lvm with SSD cache few years, but time to time I have problems with loads after reboot. If forgot about reboots all work great with LVM raid + LVM cache. Cache can be configured without raid. And you can add or remove cache in any time. Docs: https://man.archlinux.org/man/lvmcache.7
Insert logs in pastebin.com and attach links and you can open ticket on git.
You can use postfix + dovecot + roundcube + spamassassin + opendkim + pigeonhole. Maximum stability. Roundcube have aliases plugin.
You can start from here: https://wiki.archlinux.org/title/Virtual_user_mail_system_with_Postfix,_Dovecot_and_Roundcube
Topic starter don’t use docker containers. He use lxc containers. LXC is virtual machines on host kernel. Case is that: He have 3 virtual machines with shared disk. In 3 VMs have 3 different applications. Applications work under different users and can’t rewrite data on shared disk. That is user permissions problem.
the idea is that: all your applications work under the same user. or at least under the same group. because this is exactly how the differentiation of rights is applied.
A good plan is to create some kind of user in all three containers and run qbittorrent, samba and the third application under it.
A bad plan is to run everything under a random user with 777 rights, but this is a really bad plan.
Create a user in all three containers and work under it. That is not hard. Run qbittorent with that user. Config will be there: /home/user/.config . Then set that user for samba. I don’t know third app , but I think you can find how change user in manual.
You can use Revolt. Literaly Discord clone. https://github.com/revoltchat
In general, this is of course 100% based on speculation, but I assume that you can connect to a VPN but you cannot access any resource inside the local network. Just because this is the most basic mistake that beginners usually make. And it’s related to the fact that your pi is not your default gateway. To solve this, you need to enable SNAT on the local Pi interface. There are many guides on the Internet on how to do this.
P.S. Unfortunately, I have a poor telepathy skill, so it would be good to get a little more background. At least an accurate description of the problem. =)