In the linked tickets, deprecation warnings were added for various situations. ActiveSupport has a system for handling deprecations which seems to be decently described in https://everydayrails.com/2021/07/31/rails-custom-deprecation-warnings.html. It would probably be beneficial for Mongoid to use it instead of simply calling Logger#warn.

One caveat here is the log destination - ideally Mongoid's logger and AS (via Rails) logger are the same, hence the destination would be the same. If not this would need to be thought out.

shields@tablecheck.com remarked in https://github.com/mongodb/mongoid/pull/5040:

By default ActiveSupport::Deprecation.warn is going to use Rails logger with a fallback to $stderr. However, it looks that there is a way to add a Mongoid-specific behavior that would use Mongoid's logger.

The rest of the codebase should be audited for deprecation warnings also as part of this ticket.