re: Is there a password manager that allows mass or bulk password changes?

LastPass could change passwords on most websites in an automated fashion. I use BitWarden now, which cannot do this.

I suggest importing your vault into LastPass, running the process to mass change those passwords passwords, then export the vault into your vault of choice, and delete the LastPass vault. I'm not as down on LastPass as most, but to each their own.

However, the varying password rules of even mainstream sites are so shitty (no longer than 12 characters, no longer than 16, must include special characters but not !$ or &, no repeating characters, etc.) that you may have to change a bunch of them by hand anyway.