I now have the same issue as pederbar here.
I'd like to restore 1.8.19 as well, but I deleted the install files upfront. Does anyone have links, because I can't seem to find any, other than customized version at sites like XDA.
Did the same; first installed 1.8.26, then flashed Tytung r11 update (without reboot) and there it was.
Also had to change mac-address in my wireless router, r11 has a new mac-address, and I am filtering!