I am still on the test channel for GS290. All updates went fine, but the one from 20210327 runs forever. I entered the pin as requested before starting android, but then it only shows the eOS logo with the jumping dot.
If it simplifies my issue, I would be willing to switch to the dev version, now 
How should I resolve this issue?
I should add that I can reach erecovery.
Is it safe to flash the old test version (a 0.13, over the failing 0.15 from 20210327)? If so, where can i find it?
Hello @sve,
what do you think is the advantage of /e/OS test version?
Why don’t you reinstall e-0.13-q- or e-0.15-q- ‘dev’ or ‘stable’ version via Easy Installer - v.012.2-beta?
I was in a small group of volunteers that helped to test before the first release for GS290 Afterwards, I was too lazy to switch channels because you cannot switch channels without losing your data (you must backup; or has this been changed?).
Now, that I am stuck with an unusable device (without recent backups 
), I would like to stay on the test channel for obvious reasons and switch after having a recent backup.
Does anybody have the exact version string for the last 0.13 test version? https://images.ecloud.global/test/GS290/ is not browsable. Please help me.
I see no obvious reasons. Please clarify. Have you reported this on Telegram/Testing?
Can you ask a direct question of the individual who recruited you to “testing”.
It is a hard world in testing land! . You need to decide if you can risk losing your data. It is very difficult to answer the question, can I save my data and my phone!
I can see all the problems you report are valid. 
I need to make a backup from a working test release. Then, I can switch to the dev channel and start with empty data and restore my backup. That is my (limited) understanding so far.
No. The telegram group that was used back in November is shown as inaccessible; its name was “/e/ Testing Group”.
Should you research if it is possible to make some sort of emergency backup via a PC? Is the phone accessible via adb? Is a backup the most_important_thing now?
Yes, I can reach eRecovery 0.16 on the phone, and adb will work, but adb devices shows my device as unauthorized, so I have no idea how to backup without getting back to the working test version.
The problem has been solved by a new test version that I could install from eRecovery via adb’s sideload. For details, see bug 2916 linked above.