Hehe manjaroty
You can certainly install some Linux on it (Raspian is Linux) and then just tinker around. Check how much RAM it actually has and see which apps work on it.
I clicked the link and read the site and still have no idea what that is
I do that at work with Jira tickets
It's absolutely not "as left as it gets"
Not sure it's a fitting term. Most instances aren't communities. They provide their service, but there's no "we are the members of mastodon.community and here's what we do as a community". They exist but aren't the norm. Calling instances communities probably leads to wrong expectations
This thread has some nice posts on how to live "more solarpunk" by yourself, but IMHO solarpunk is more than that. Finding/founding and participating in all kinds of neighborly/local groups is another big factor which plays a big role in resilience. Community gardens, people's kitchens, cultural groups etc. Community is important. Can also be connecting to your neighbors in other ways.
KYC = know your customer
For everyone else but knowing
You need a reserve proxy. That's a piece of software that takes the requests and puts them toward the correct endpoint.
You need to create port forwards in the router and direct 80 and 443 (or whatever you're using) toward the host of the reverse proxy and that is listening to on those ports. If it recognized the requests are for nas.your.domain, it will forward the requests to the NAS.
Common reverse proxies are nginx or caddy. You can install it on your raspberry, it doesn't need it's own device.
If you don't want that, you can create different port forwards on your router (e.g. 8080 and 8443 to the Raspi) and configure your service on the Raspi corresponding. But it doesn't scale well and you'd need to call everything with the port and the reverse proxy is the usual solution.
Solarpunks can have a little downtime, as a treat

