This is a binary choice: Trump or Harris. No third-party Presidential candidate has any chance of winning.
‘I can’t commit to voting for Harris because I need to know more about her policies’ is always disingenuous. Either the speaker is trying to fool those listening, or he is trying to fool himself.
Harris has been in public life for long enough to indicate how she will govern and what policies she will pursue. If we don’t know every detail of how those policies will read, then we are living in the same reality we’ve been living in for every other Presidential election.
Declining to vote for Harris over some perceived ‘lack of information’ about her policies means that the voter is supporting Trump. It truly is as simple as that.