I have a Server with ~16 podman services, each their own user, network namespace and uids. This is managed using NixOS and Home manager (which supports quadlets) but I am changing my setup to a single node k3s cluster with user namespaces because that seems simpler to manage. Here a snippet for how the subuids/subuids are defined:

users.users.<username> = {
        subUidRanges = [{
            startUid = 100000+65536*( config.users.users.<username>.uid - 999);
            count = 65536;
        }];
        subGidRanges = [{
            startGid = 100000+65536*( config.users.users.<username>.uid - 999);
            count = 65536;
        }];
        home = "[...]";
        isNormalUser = true;
        linger = true;
        group = "users";
        openssh.authorizedKeys.keys = config.users.users.root.openssh.authorizedKeys.keys;
    };

How are you running podman? As a rootful systemd service or as a rootless user systemd services?

If you have an openwrt compatible router then you can use that as the tang server.

Also you can tell clevis to use both tpm and tang and require both to work.

Straight to jail

I use bitwarden send, all my devices already have access to my password database and i can save and download files or text though it. You can also use the URL to let other devices access it if you want.

Use a VPN, it’s not ideal but it’s secure.