The click/8.3.0 release made changes to APIs b-m-v relies on. In my specific case, ConfigOption overrides process_value(), and makes the assumption that 'value' is a str - which is no longer true.

You can see discussion/resulting-stacktrace here: pallets/click#3065 (comment)

You can see the (small) amount of digging I did here: pallets/click#3065 (comment)

And you can see the Click Gang's response here : pallets/click#3065 (comment)