Woooh …
I withdrew a post as I had not fully read today’s episodes!
@mailanmitch If there are hidden identical commands on the system, “what can anyone expect?”
My early link does reveal the source of earlier version.
PS Yes, restart the laptop! But you should not introduce another identical command.
If the new folder ends up in the same place it will put it back in PATH position…I think. and which fastboot should check
Sorry, I don’t know what you mean. Best if I leave alone .
In general in Linux we do not have to restart the computer, but with Android Bridge in my opinion we have a very complex situation with permissions, which Ubuntu does not always get right.
My workflow would be to remove system platform-tools and restart.
@chrisrg, I am very sorry that in my haste to react, I seem to have made a “reply_to_you” that was quite unintentional! Sorry.
OK, I have deleted the version 31.02 and renamed the 30.05 into “/home/mitch/platform-tools”
If I press “fastboot – version” it confirmed: fastboot version 30.0.5-6877874
If I now enter “flash --disable-verity --disable-verification boot boot.img” nothing really happened. The cursor moved to the next line and I cannot go back with the arrow keys (only strange signs appear like ^[[B^[[A^[[D^[[C"
Besides nothing happened. Do you know what happened? Shall I close terminal and try again?
HI @aibd @chrisrg , forgot to mention in my last post: I had restarted the computer but it didn’t change anything. Same error message, Therefore I installed 30.05 now (see previous post)
Did you miss fastboot off the front of the command?
Sorry that was just a copypaste bug, I entered “fastboot flash --disable-verity --disable-verification boot boot.img”
I am afraid I have to say that I regard GS290 as fragile.
@mailanmitch I have to say I would much rather I was helping you do adb push and pull or something quite harmless, rather than hacking a nearly new phone.
Here is a proposal. @mailanmitch, please could you cd in your working folder and do
ls -l
Just so we all know what we are dealing with.
mitch@mitch-InfinityBook-S-14-Gen6:~/platform-tools$ ls -l
insgesamt 2426008
-rwxrwxr-x 1 mitch mitch 7262264 Okt 2 2020 adb
drwxrwx— 2 mitch mitch 4096 Okt 2 2020 api
-rw-rw-r-- 1 mitch mitch 33554432 Mai 9 22:12 boot.img
-rwxrwxr-x 1 mitch mitch 59512 Okt 2 2020 dmtracedump
-rwxrwxr-x 1 mitch mitch 1585992 Okt 2 2020 e2fsdroid
-rwxrwxr-x 1 mitch mitch 309080 Okt 2 2020 etc1tool
-rwxrwxr-x 1 mitch mitch 1942192 Okt 2 2020 fastboot
-rwxrwxr-x 1 mitch mitch 13696 Okt 2 2020 hprof-conv
drwxrwx— 2 mitch mitch 4096 Okt 2 2020 lib64
-rwxrwxr-x 1 mitch mitch 258032 Okt 2 2020 make_f2fs
-rwxrwxr-x 1 mitch mitch 257488 Okt 2 2020 make_f2fs_casefold
-rwxrwxr-x 1 mitch mitch 873440 Okt 2 2020 mke2fs
-rwxrwxr-x 1 mitch mitch 1157 Okt 2 2020 mke2fs.conf
-rw-rw---- 1 mitch mitch 388260 Okt 2 2020 NOTICE.txt
-rw-rw-r-- 1 mitch mitch 18272256 Mai 9 22:12 recovery-e-0.14-q-2021012698290-dev-GS290.img
-rwxrwxr-x 1 mitch mitch 1539624 Okt 2 2020 sload_f2fs
-rw-rw-r-- 1 mitch mitch 38 Okt 2 2020 source.properties
-rwxrwxr-x 1 mitch mitch 1372144 Okt 2 2020 sqlite3
-rw-r–r-- 1 mitch mitch 2416493196 Apr 23 03:08 system.img
drwxrwx— 3 mitch mitch 4096 Okt 2 2020 systrace
I reopened terminal and typed the usual command (fastboot flash --disable-verity --disable-verification boot boot.img) now it says:
< waiting for any device >
If I enter: “fastboot devices” it states
GS290CTM701899 fastboot
OK, but the correct workflow would be
fastboot devices
fastboot flash --disable-verity --disable-verification boot boot.img
Does that make any difference?
No, unfortunately not. Still, < waiting for any device >
So you are seeing
fastboot devices
GS290CTM701899 fastboot
fastboot flash --disable-verity --disable-verification boot boot.img
waiting for any device
In which case it seems to me the second command is not seeing a “target”. I cannot explain that atm.
Yes, that is exactly what is on my terminal screen.
Cable! That was the result of searching your error. 
Phew! Could it be?
And try another usb port also (if available)
Guys, this is crazy! It worked out - I have /e/ on my GS-290! 
I can’t believe it - but it apparently was indeed the cable!!! Please note that I had used the original cable delivered with the GS-290. I have now exchanged it with the original cable from another mobile.
Summing up what (probably) happened (maybe interesting for other users):
Error message 1: “fastboot: error: cannot load ‘boot.img’: No such file or directory”
This was caused by an absolute beginners’ bug on my side (executing the command from the wrong working directory)
Error message 2: "“: terminating with uncaught exception of type std::out_of_range: basic_string Abgebrochen”
This was probably solved by changing from the latest ADB version (31.0.2) to ADB version 30.0.5 (plus maybe removing conflicting fastboot & adb files which came with the Linux system)
Error message 3: “< waiting for any device >”
This was apparently in my case caused by a not 100%-functioning original cable from Gigaset (although the phone was recognised with fastboot devices). Solution was to take a different cable.
Thank you so much @aibd and @chrisrg, and also @Ingo_FP_Angel - for the time and efforts you have taken to help me! 
Without you I would doubtlessly have been totally lost in this.
I have really learned a lot - and still remain a beginner. But a beginner with a self-flashed /e/ GS290 