I used the suggestions at your last link to launch Brave from the command line.
/opt/brave.com/brave-nightly/brave -n --args --incognito --no-experiments --disable-extensions --disable-gpu
When I attempt to download your testFile.txt link, the following error is displayed in the terminal window each time the download is attempted:
Gtk-Message: 17:26:25.240: GtkDialog mapped without a transient parent. This is discouraged.
EDIT TO CLARIFY: It repeatedly reports the following error, EVEN IF DOWNLOAD has NOT been attempted:
[34447:34447:0406/173350.374388:ERROR:star_randomness_points.cc(120)] StarRandomnessPoints: no response body for randomness request, net error: ERR_HTTP_RESPONSE_CODE_FAILURE
There is also some startup errors:
MESA-INTEL: warning: Ivy Bridge Vulkan support is incomplete
libva error: /usr/lib/x86_64-linux-gnu/dri/iHD_drv_video.so init failed