Put random stuff as the security answers in my Trial World of Warcraft account in 2005. In order to merge it into my Battle.net 2.0 account around 2009 I needed to know it, and even though I had the correct password there was no way to change security questions and I had to beg customer support (which was a long process, involving software serial numbers, scans of ID, the whole works).
Ultimately they told me what my mother's maiden name was: qewqewdfskjr3924kjasdf
I assume when people suggest putting random strings in these fields, it's implied that you're supposed to save that data in a password manager or something. Mine (KeePassXC) supports storing arbitrary data as "notes" in each entry, along with TOTP information (great as a backup in case you lose your phone), and other stuff.
I worry more that a particularly dull customer support agent is likely to be convinced by a random caller to reset the password if they can see that those fields are garbage.
Use randomly generated words. A CSR might be convinced by "idk I just put random words in there LOL" when the security question answer is uaisehf8wefjh0824m, but if they see "correct-horse-battery-staple" as the answer, it might be a bit harder to convince.
This is what I do, although like others mention I still use real words. I add my bogus answers to security questions as notes in my password manager. This method has worked well for me for a long time without any risk that I have discovered.
Put random stuff as the security answers in my Trial World of Warcraft account in 2005. In order to merge it into my Battle.net 2.0 account around 2009 I needed to know it, and even though I had the correct password there was no way to change security questions and I had to beg customer support (which was a long process, involving software serial numbers, scans of ID, the whole works).
Ultimately they told me what my mother's maiden name was: qewqewdfskjr3924kjasdf