I just built TWRP for Teclast M30 and it seems working correctly. Please try if you want.
First, you have to unlock bootloader. Unlocking bootloader can be done with fastboot.
Flash the img file using fastboot during fastboot mode:
$ fastboot flash recovery twrp~~.img
After done flashing, reboot to recovery and TWRP will come up.
If you have any questions, please mention/DM me on Twitter.
- Extra info about GSI
While Teclast M30 is released with Android 8.0 preinstalled, the device is Project Treble capable. You can check Treble checker apps if you doubt.
So, GSIs can be installed. You can try ARM64 A-only
images. I tried LineageOS GSI (Android 8.1), Havoc OS GSI (Android 9.0) and many GSIs listed on phhusson's GSI list, they're working well (except Android 9.0 GSIs, they have Bluetooth discovery issue). Android 10 GSIs are not working, since they're stay forever in booting logo.