These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.95 s (backtrack: 0/20).


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by sci-chemistry/avogadro2-2.0.0::gentoo
# required by =sci-chemistry/avogadro2-2.0.0 (argument)
>=sci-libs/avogadrolibs-2.0.0 qt6 archive

 * In order to avoid wasting time, backtracking has terminated early
 * due to the above autounmask change(s). The --autounmask-backtrack=y
 * option can be used to force further backtracking, but there is no
 * guarantee that it will produce a solution.

!!! All ebuilds that could satisfy "sci-libs/inchi" have been masked.
!!! One of the following masked packages is required to complete your request:
- sci-libs/inchi-1.07.5::gentoo (masked by: IUPAC-InChi license(s))
A copy of the 'IUPAC-InChi' license is located at '/Volumes/Disk 1/Repository/portage-git/licenses/IUPAC-InChi'.

- sci-libs/inchi-1.06-r1::gentoo (masked by: IUPAC-InChi license(s))

(dependency required by "sci-chemistry/openbabel-3.2.1::gentoo[inchi]" [ebuild])
(dependency required by "sci-libs/avogadrolibs-2.0.0::gentoo[qt6]" [ebuild])
(dependency required by "sci-chemistry/avogadro2-2.0.0::gentoo" [ebuild])
(dependency required by "=sci-chemistry/avogadro2-2.0.0" [argument])
For more information, see the MASKED PACKAGES section in the emerge
man page or refer to the Gentoo Handbook.