I found the cause: I had used German special characters in my gmx password. After I changed the password, configuring Dekko was no problem at all -- it did not even show that "Server Configuration" screen.

One possible explanation: The "German" characters on the UT keyboard only look right, but they are not actually German characters. For example, the ü is also used in the Turkish alphabet, where it looks exactly the same.

I know from Russian characters that the cyrillic e looks exactly like the Latin e, but is not recognised by web searches as a Latin e. So maybe gmx does not recognise the ü froum Ubuntu Touch because it is another ü than the one from a German keyboard.

EDIT: The UT keyboard does not seem to be the cause: I copied the password from my computer into a text file and from there into the Dekko configuration -- still did not work. So I guess there must be some problem with Dekko transferring German Special Characters in logins to the mail server.

@keneda Thank you! Strangely, I tried it again and it worked. The only thing I did differently this time was to create a small contacts.db (mine is 1.8 MB so I thought that the size might be the problem), move it into the directory and after a restart the contacts were shown. Then I deleted it, moved my 1.8 MB contacts.db into the directory and it worked. I have no idea why. I don't think my antics with the smaller file had anything to do with it. Anyway, thank you: Without your insistence that the contacts are saved in contacts.db I would not have tried it again.

I'm sorry for asking this question that has probably been answered in many posts, but I can't find them:

How can I connect my phone to my (Linux Mint) computer?

I disabled ufw, started ssh on the phone and I guess I have to change some entries in etc/ssh/sshd_config, but with my limited skills, all I managed to achieve were refusals and denials:
ssh: connect to host 192.XXX.XXX.XX port 22: Connection refused
or
phablet@192.XXX.XXX.XX: Permission denied (publickey)

What do I have to do?

@moem said in How can I connect a Linux computer via ssh / openssh to a Ubuntu Touch phone?:

Have you seen this manual?
https://docs.ubports.com/en/latest/userguide/advanceduse/ssh.html

That's exactly what I was hoping for. Great, thanks!

@arubislander Well, you can just use the commands "sudo ufw enable", "disable", "status" etc. However, I'm not sure it is enabled by default and - in case it's not - if one is supposed to enable it. As I then realised, it also blocks the browser and dekko; it was impossible to go online with ufw enabled. So in the end I switched it off for good. EDIT: Only later I read in this forum that 1. things are complicated with the ufw and 2. the firewall is inactive since all ports are closed by default. And indeed, according to nmap, all 65355 ports are closed, except for the one specified for ssh (only as long as ssh is running).

I cannot set up Axolotl because at the point where you're supposed to get the code (probably via SMS, at least that's how it's on the Pinephone) nothing happens: No SMS, no code.

Is there anything I could do?

@messayisto Yes, that seems to be right. If I understand the Telegram channel correctly, the registration issue persists, but the relentless & much appreciated devs are working on it. The problem will be fixed in a version that will only work with UT 20.04.