M1 MacOS no longer allows external startup boot drives?

That seems to be the case. I've been struggling for a week to create a second, external boot disc for my M1 Mini, without success. The lack of success is in both creating a boot disc and in changing the M1 security settings to accommodate an external boot drive. The "startup disc" preference is still a feature of MacOS System Preferences, whether an auxiliary boot disc can actually be employed or not, but the facility for creating one is, frankly, crippled. I have gone through the process: download macOS Monterey installer, save to Applications, select, erase, reformat external target disc, install--over and over and over, to no effect at all. What winds up on the target disc is clearly inadequate, and every time I try to declare such a disc an alternative for "Startup disk", the system tells me that the disk is either damaged or incomplete. It's pretty obvious why, considering that the only folder on the disc that has any contents is "System". The others are empty. So I ask you, where is this mysterious "alternate" startup disc supposed to come from? Do I need to go out and buy one from Apple? What's worse, for me, is that none of the usual sources of information-these forums, AppleCare, or the local Apple Store "Genius Bar" can tell me squat about it. I've received either no help or wrong information from all of them. In many of those cases, I had trouble making them (the specialists) understand why I would want to create an external boot drive, i.e., a "Startup disc", in the first place. If they don't get it, If it's such an outlandish notion, then why is that option still available in System Prefs? Is the-granted-more complicated OS designed to restore and repair severely damaged boot drives without necessitating reformatting the disc-is that intended to do away with the need for an alternate startup disc? If a damaged drive were the only circumstances necessitating an alternate boot drive, that would suffice, but there are other reasons for wanting an alternate drive. Apparently that option is no longer available on M1 Macs.