I dont recall deleting bad questions (and dont have the rep to see my deletions), and I've been using Stack Exchange for many years, paying attention to Meta, creating and reading Meta questions asking best practices, and while

I definitely can recall a few guilty Stack Overflow questions where I was asking something too broad out of desperation to solve a confusing problem, I think my activity on SE is pretty mindful of quality overall.

Are you question banned on Super User or Stack Overflow. Question bans are separate to individual communities. You certainly don’t have the best track record for asking questions here a Super User. Asking clear precise questions is very important.

Question bans only happen after a continued verifiable pattern of asking questions that have been poorly received by the community. The amount of questions that have to be poorly received is extremely variable, but question bans, never happen after only a handful of questions.

Can someone with enough rep remind me what horrible deleted question lurking in my past here is the culprit of my permanent ban from the site?

You can access that yourself here or at least the questions deleted in the last 60 days.

Not great, lots of questions with no upvotes, but only 1 downvoted question of 11 total.

Every question that was closed and then deleted for inactivity, deleted by the moderators for quality reasons, or by yourself for any reason count against your ability to ask another question.

You will be able to ask another question 6 months from when the ban started. Your last question was in May, 6 months from that, would be around November 19th 2020.

Your case is probably borderline to be honest. I cannot search for your deleted questions, a moderator could perform that search, but question bans do not happen unless there is a pattern of poorly received questions.

I dont recall deleting bad questions (and dont have the rep to see my deletions), and I've been using Stack Exchange for many years, paying attention to Meta, creating and reading Meta questions asking best practices, and while

I definitely can recall a few guilty Stack Overflow questions where I was asking something too broad out of desperation to solve a confusing problem, I think my activity on SE is pretty mindful of quality overall.

Are you question banned on Super User or Stack Overflow. Question bans are separate to individual communities. You certainly don’t have the best track record for asking questions here a Super User. Asking clear precise questions is very important.

Question bans only happen after a continued verifiable pattern of asking questions that have been poorly received by the community. The amount of questions that have to be poorly received is extremely variable, but question bans, never happen after only a handful of questions.

Can someone with enough rep remind me what horrible deleted question lurking in my past here is the culprit of my permanent ban from the site?

You can access that yourself here or at least the questions deleted in the last 60 days.

Not great, lots of questions with no upvotes, but only 1 downvoted question of 11 total.

Every question that was closed and then deleted for inactivity, deleted by the moderators for quality reasons, or by yourself for any reason count against your ability to ask another question.

Your case is probably borderline to be honest. I personally cannot search for your deleted questions, a moderator could perform that search, but question bans do not happen unless there is a pattern of poorly received questions. It appears you have asked 24 questions, 13 of those questions have been deleted, which means more than 50% of the questions you have asked have been deleted.

You will be able to ask another question 6 months from when the ban started. Your last question was on May, 6 months from that, would be around November 19th 2020.