I've been trying to install support for ECW so I can load them in latest QGIS 3.6 (also tried in QGIS 3.4.4)

Having tried the following tutorials:

https://wiki.openstreetmap.org/wiki/ECW (gdal 2.2.3)

https://gist.github.com/1papaya/568c4580b1909071696c1cb119101823 (gdal 2.3.1)

Both appear to work and report back ECW support against gdal

gdalinfo --formats | grep ECW
ECW -raster- (rw): ERDAS Compressed Wavelets (SDK 3.x)
JP2ECW -raster,vector- (rw+v): ERDAS JPEG2000 (SDK 3.x)

However when opening QGIS I notice that key UI is missing - the little triangles next to all the processing toolbox processes are missing, and the whole of QGIS becomes unstable - for example it crashes to desktop when selecting plugins within the plugin manager.

I then have alot of trouble recovering QGIS to get the UI back - full removal and purge of all dependencies + QGIS reinstall does not restore it! have to carry out full ubuntu reinstall to get it all back, which is not ideal.

Is gdal completely independent per version install. as above tutorials focus on particular gdal download which you then appear to manipulate?

QGIS 3.6 appears to use gdal 2.2.3

QGIS 3.4.4 appears to use gdal 2.4.0

so far I've carried out above tutorials first then installed QGIS, should I perhaps install QGIS first then attempt to adjust the GDAL that QGIS installs as a dependency?