lv2-1.2.0 was installed on my amd64 system (1.2 was unmasked). Ardour-3.5.14 build failed instead of complaining that lv2-1.4 needs to be unmask. This seems to be a missing dependency in the Ardour ebuild. Best regards Martin Erdtmann
I am sorry, it must be Ardour-3.5.14.
Thanks for reporting! This is fixed now in 3.5.14 and 9999 as well as in the freshly bumped 3.5.74. Have fun! :-)