I suppose I’d rather know that and be able to factor it in to my schedule, irritating as it is, than not know and get caught by the month-long delay.
Given free rein, I’d absolutely love to tell people that needing me to show them how to do X in Excel is actually not a vacation-interrupting emergency and there are tons of free videos that would explain that, if they did not want to contact the actual departments who handle tech support and training. Or that this project they’ve known about for a month but decided to keep under their hat until it became an emergency is something they’ll need to resolve themselves. But that would not fly at all.

Hah! Maternity/parental leave is often 1 year here, so there is zero expectation you will read or “catch up” afterwards. We keep our email addresses during where I work (Canadian government), so it’s standard to put an OOO that just says “on parental leave. Please contact X instead” with no reference to actually reviewing any of those emails, and often not even a projected date of return since people often flex their return date or take extra time, or just return to a different position entirely (out of choice).
Use your absence as an opportunity to show off to customers and peak their interest in your content. Sending an out-of-office email is a good way to provide clients with more details about your business. Offer a link to an interesting online resource that your company has developed, like a blog post. This way, recipients are made aware of which lines of business your company are actively engaged in.