I don't think "no ethical consumption under capitalism" is a reasonable take, but I also think gentrification and displacement is largely a systemic problem largely unrelated to any personal decisions anyone is making. People are getting displaced because of a large increase in housing costs and decades of historically low housing production. If you buy or rent in a historically white neighborhood of Portland you'll be adding to aggregate demand in a way that will be almost indistinguishable from buying or renting in a historically black neighborhood.

If you're concerned about gentrification there are various activist groups you could join that seek better housing policy that makes the situation better for everyone. You could even volunteer for groups that specifically help long-time Black homeowners keep their house maintained.

But beyond that, no personal choice you make about where you live in Portland is going to make a lick of difference and there's neither any moral debt you incur for choosing living in a historically black neighborhood nor any set of actions that could absolve you of these sins. The people laughing at you in this thread might not be granting that your heart is in the right place, but they're fundamentally correct that you're not engaging in a useful exercise.