Actually I do have a suggestion. When I’m asked to do something that I think is pointless I go full nice, but rational mode. Keep asking questions as if you’re trying to understand their request. And as you keep asking why this way and not that way they may end up realising how ridiculous they sound and drop it or accept an easier alternative. It may be important to avoid gloating and to propose your preferred solution (available by phone) as a suggestion to help them save face. The way to work with crappy managers is to keep them feeling good about themselves. You can use that to your advantage. It sucks and it may not work but there’s only so much you can do.
Why not use KeepassXC? It’s a completely local encrypted db but it integrates with cloud storage apps like nextcloud for sync. It has plugins for integration with Firefox and KeepassAndroid is pretty smooth on the current Android OS.