Selfhosted

I'm looking for advice to maximize security.

The most important answers to this all live outside your server. What is your home network like? Do you control the gateway? Do you have a dedicated firewall? Do you have devices segregated into VLANs so they can't observe each other (especially IoT devices)? Do you have SNMP disabled?

1. Containers are not a security barrier. They cannot be, they never will be.
2. If you are defending against intrusion at your local file server, it is already too late. The call is coming from inside the house.

If you want security, you block all inbound and outbound traffic by default at your network firewall (not the server OS firewall), and then you open only the ports that you actually need, one by one. You set all the closed external ports to do not respond ("stealth" mode), so that anybody trying to reach your network from outside just gets nothing back except on the ports you specifically need to use. You segregate your internal network into logical areas, and you put things that need to talk to each other on their own VLAN, which may or may not have access to the upstream WLAN trunk depending on what they're doing. You don't allow crosstalk between VLANs except in very specific cases. You set static IPs and document them, so that you never have to ping or traceroute internally to find something, so you don't need SNMP. Anybody trying to use SNMP is conducting surveillance on your network and should stick out from other traffic (some "smart"/IoT devices do this automatically - they are bad and should be treated as malicious and should not be allowed to phone home). And then you monitor your traffic at the firewall, and you deal with anything unexpected as it comes up (like once a week review the logs until you have a sense of what normal looks like on different days at various times, then maybe set a few automatic alerts for things that exceed normal-ish boundaries, then go to reviewing like once a month or so - you don't need to be checking your logs hourly unless you have some reason to be actively paranoid).

If you handle everything correctly at the router/firewall level, you're way way beyond the security of most residential and small business networks. You're not, you know, impenetrable, but you're at the point where somebody with experience and resources will have to be trying to break into your network specifically on purpose. If you're that kind of target then nothing short of an actual SOC is going to help you, and running self-managed servers on your home network is a bad idea.