10 bit color on Linux with Intel HD video card, my study

Today (Feb 2016) I answered for myself if there is a 30-bit (10-bit per channel) color support on Linux with Intel HD graphics. I'm an owner of Dell U2413 which is capable of deep color (still I wouldn't recommend this monitor because of the brighter corners and big pixel size). There is no Nvidia Quadro in my disposal and I tried Linux setup with "Depth 30/DefaultDepth 30" in xorg.conf. Running Xorg in this mode on Intel HD 5000 is fine, but according to "Deep Color Support of Intel® Graphics Technical White Paper revision 0.8" (copy here: http://xvi.crypts.me:5081/deep-color-support-intel-graphics-paper.pdf very interesting reading, my respect to Intel engeneers)

"There is no OpenGL support for 10/12 bit with Intel graphics driver. Intel will reevaluate this as the technology matures."

Which means Gnome3/Unity and other Linux desktops with approach "old hardware must R.I.P." are painfully slow. Even with llvmpipe driver it's unusable. Gnome3 complained it had not found texture from pixmap. GTK2 apps are unusable because of smashed colors. KDE had problems. The only variant that worked for me was Fedora 23 Mate (build on GTK3, not GTK2). It's fast, colors are ok. I tried Rawtherapee - loaded fine with some mixed colors, but only black areas instead of images. Very sad. Krita was capable of displaing images, but pointer over an image became very slow, which means it was renered with OpenGL. No signs of 10-bit color on test images.