Duh, tonight, I restarted the installation (out of docker) on my Pi, this time also not using the nvm installation I had in /root (I created a dedicated account for that purpose).
This seems to work, woohoo!

Clearly, following exactly what's written at https://github.com/staltz/easy-ssb-pub (last paragraph)... just worked!

Now I wish I could also launch an sbot command at bash...

You can try to connect and get an invite at http://pub.appreciatingsystems.com:81/.

Now I need to find that script to check whether the server's still alive or not...

Tonight I created a fresh user on my raspberry pi 3B raspbian. I followed the installation instructions for easy-ssb-pub, edited src/config.js to change the web port from 80 to 8000 (thus not requiring root privs), did npm install and then launched with HOST=pub.appreciatingsystems.com npm start.
(oh, before that, I copied my previous .ssb/secret file)

After a while, usually after the first request on the web page, it crashes:

/home/ssbpub/easy-ssb-pub/node_modules/epidemic-broadcast-trees/stream.js:75
      state.msgs.length || state.notes
            ^

TypeError: Cannot read property 'msgs' of undefined
    at EBTStream.canSend (/home/ssbpub/easy-ssb-pub/node_modules/epidemic-broadcast-trees/stream.js:75:13)
    at EBTStream.resume (/home/ssbpub/easy-ssb-pub/node_modules/epidemic-broadcast-trees/stream.js:83:14)
    at EBTStream.pipe (/home/ssbpub/easy-ssb-pub/node_modules/push-stream/pipe.js:18:25)
    at module.exports (/home/ssbpub/easy-ssb-pub/node_modules/push-stream-to-pull-stream/source.js:32:8)
    at Function.module.exports [as duplex] (/home/ssbpub/easy-ssb-pub/node_modules/push-stream-to-pull-stream/duplex.js:6:13)
    at EventEmitter.<anonymous> (/home/ssbpub/easy-ssb-pub/node_modules/ssb-ebt/index.js:104:22)
    at EventEmitter.emit (events.js:164:20)
    at setupRPC (/home/ssbpub/easy-ssb-pub/node_modules/secret-stack/index.js:207:13)
    at /home/ssbpub/easy-ssb-pub/node_modules/secret-stack/index.js:231:45
    at next (/home/ssbpub/easy-ssb-pub/node_modules/multiserver/compose.js:28:14)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! easy-ssb-pub@4.0.0 start: `tsc && node dist/index --host $HOST`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the easy-ssb-pub@4.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/ssbpub/.npm/_logs/2019-03-01T21_42_23_293Z-debug.log

I just tried to launch easy-ssb-pub on my ubuntu, and I get a crash when trying to generate an invite. Log is below. my laptop's name is "portable" so I did "HOST=portable docker-compose up -d" (as root)

Any idea?

TypeError: Cannot read property 'match' of undefined
at Object.isPrivate (/usr/src/app/node_modules/ip/lib/ip.js:262:15)
at Object.<anonymous> (/usr/src/app/node_modules/scuttlebot/plugins/invite.js:81:40)
at apply (/usr/src/app/node_modules/muxrpc-validation/index.js:173:15)
at Object.<anonymous> (/usr/src/app/node_modules/muxrpc-validation/index.js:82:14)
at Object.hooked [as create] (/usr/src/app/node_modules/hoox/index.js:10:15)
at readInvite (/usr/src/app/dist/http.js:40:21)
at /usr/src/app/node_modules/pull-stream/throughs/take.js:27:9
at next (/usr/src/app/node_modules/pull-stream/sinks/drain.js:16:11)
at sink (/usr/src/app/node_modules/pull-stream/sinks/drain.js:37:9)
at pull (/usr/src/app/node_modules/pull-stream/pull.js:41:14)