It is now 8 months since a manuscript of mine submitted to a major journal has gone without peer reviewers being found, and 2 months since a query to the editors asking for an update has gone without a response. Is this the norm, now?

Should definitely not. Would consider resubmitting elsewhere, if that is an option for you

Withdraw it

That’s pretty egregious.

agree with others: PR can take a really long time, but editors should be prepared to be responsive and transparent about that. a lack of care for you as the author at this stage implies a lack of care for your work at a later stage