Can I ask my advisor to drop authorship for a journal submission?
This is not about the relationships with the former advisor at all.

The list of authors is supposed to be determined based on who actually worked on the particular research (which sometimes – however good or bad it is – may mean simply being a supervisor and providing funding). If the researcher contributed to several of


the formulation of hypothesis
data collection / measurements / numerical simulations
data analysis
writing the actual paper
insert here other field-specific steps


she should be an author. Certainly, different criteria for being an author of the paper can be applied, and the list is very field-dependent.

However, the unfortunate amalgamation of facts that


you want to submit to a certain journal X
this journal X has a certain conflict of interest policy
the presence of one co-author who normally would be listed in the list of authors does not allow to submit to X


should not be used as a reason to exclude one from the list of authors. At least, the initiative should not come from the other authors who could benefit from it.



So, I would strongly consider submitting to a different journal.

Alternatively, you (or your colleague in the potential conflict of interest) can ask the journal X editor to arrange a submission/revision process through another associate editor(s). There might be other associate editors willing and qualified to do it for the paper in your field and your particular research direction.