Hello all!
I've been able to replicate this problem after fiddling quite a bit with my
Abrowser profile (mostly testing a lot of add-ons).
The solution that worked for me (restoring both the proper operation of the
"When Abrowser starts" option and the Ctrl + Shift + T shortcut, maybe
others) was to switch the "Start Abrowser in a private browsing session"
option found at the "Privacy" tab of the settings on and back off (a couple
of Abrowser restarts will be necessary), at which point the behavior went
back to normal.
I reckon this is more of a workaround than a proper fix, but still, I hope it
can help others with this problem.