can't get file transfer working. Help, please!

[awaittrot]

I tried

Code:

sshfs user@ip:/home/user /tmp/mnt

but got Connection reset by peer

Then trying to simply ssh to user@ip, I get Permission denied (publickey,keyboard-interactive).

Don't know if your last bit of code would solved that, haven't tried yet

It looks like password authentication for default user is disabled in pmOS, so this has to be enabled first. Instructions can be found at pmOS wiki.
https://wiki.postmarketos.org/wiki/SSH#First_login