I already posted that I had assembled a TeenAstro Mini and it looks like working.

As I am a Linux guy and want to be able to hack on the software, I don't want to use the prebuilt firmwares and cannot use the flashing tool for Windows.
No problem so far, as I already have the Arduino IDE installed and the installation of the Teensyduino extension ran smoothly. I can compile (with only one warning about "enumeration value 'NODRIVER' not handled in switch") the current github head and flash it to the Teensy.

Now a few questions arise regarding building from source and setting up for the mechanical properties of the telescope mount (by not using Windows, I cannot use TeenAstroConfig.exe, which aside from that, seems to be closed source):

I had set CPU speed to 72MHz and Optimize to "Faster", is that right?
As there is no other branch nor any tag set, I used the git master head; is that reasonable for trying out?

I dug into the sources a bit and it seems that the only compile time configuration is in "Pins.TeenAstro.h" and it seems that all is already set up correctly there, for the TeenAstro Mini with TMC5160 drivers out of the github master head. Am I correct with that?

All of the other configurations can be made via LX200 and are stored in EEPROM, is that correct?

I played around with the settings that can be done via LX200 protocol. For this I browsed through the sources implementing the LX200 command processing. This is a bit tedious and the commenting is not always clear enough for me to understand right away, what the command parameters represent.
So another question is, whether there exists a list of the supported LX200 commands, comparable to the one about OnStep (http://www.stellarjourney.com/index.php?r=site/software_telescope)?
If there is not, I would consider to compose such a list, but I probably needed help with some of the commands.

For playing around, I have connected a stepper motor to the TeenAstro and I can turn the shaft by M-commands, but the turn is very slow and the motor gets quite hot even when standing still. By increasing the $G setting I can increase the turning rate, but still it stays quite slow.
From what I can see in the sources, according to the comments, the command "SXE1" should "Set the MaxRate in sideral Speed" but there is no code executed at all on decoding that command.
There seems to be an acceleration/deceleration ramp when commanding a move, but the ramp is very slow, maybe a minute or so. I would expect a ramp up/down in a few seconds.

To summarize: I do not understand, what to do for that motor to work properly. Maybe I have a totally inadequate motor?
I hope that somebody can give me some hints on what could cause the observed motor behaviour.

By the way, I tried with the INDI driver as well and can observe the exact same unexpected behaviour.

thank you and best regards
Lukas