eventually I found
   from [1]https://www.rigacci.org/wiki/doku.php/doc/appunti/android/sp_fl
   ash_tool that the flasher is available for linux (binary only). if it
   works with my glibc, this could make it much easier to work with.
   I also took a usb log of the windows flasher using usbpcap. unfortunate
   since the flasher speaks in com ports.
   the links from that website jump to various shady binaries, there's
   something called "miracle box" that can flash most devices, and is
   closed source.
   my phone is no longer providing usable tethered internet (~5KB/s when
   lucky), but works fine nontethered. maybe some business agreement.
   2022-05-03 0928 ET
   so i'm downloading things to the phone and transferring them off adb,
   which for some reason does not always work, but has been recently.
   0936
   the linux flash tool launched fine on my ancient glibc, great.
   unfortunately it says my scatter file is invalid.
   on the web links they talk about generating scatter files.
   0937
   the provided sp flasher has "custom" after it. could be related.
   this flasher has more options, like readback and memory test.
   0939
   0945
   there are some example scatter files
   at [2]http://www.mediafire.com/file/md5xj1n8mdm0rf9
   my vendor scatter file is name MT6771_Android_scatter.txt
   0946
   1029
   so it turns out the partition map ("scatter file") format is forward
   compatible for _minor_ version numbers. so my scatter file for v3.2128
   does not work on v6.1520 but finally _does_ work on linux sp flash
   v5.2208 . v6 also has the issue of changing the format to xml.
   I just downloaded all the partitions from linux for the first time!
   1031

References

   1. https://www.rigacci.org/wiki/doku.php/doc/appunti/android/sp_flash_tool
   2. http://www.mediafire.com/file/md5xj1n8mdm0rf9