But that’s already a 2.x version binding and there is no legacy version of that binding. So that binding is under discussion because it will already be supported.
So far the only legacy binding you’ve listed is MQTT but you’ve not sighted any specific capability gaps, just that might be capability gaps. To the contrary as far as I’m aware, everything that the MQTT 1 binding could do the MQTT 2 binding supports as well, though per usual, how it supports it might be pretty different. For examples:
- REGEX Filter: MQTT 2.5 M1+ How to implement the equivalent to MQTT1 REGEX filters
- Event Bus: Marketplace MQTT Event Bus
- Generic MQTT Things cover the rest.
All of the major bugs and problems with the MQTT binding have to do with Homie and HA automatic discovery which are features the MQTT 1 binding does not and could not support.
So, unless there actually is some capability in MQTT 1.x that is not supported by MQTT 2.5 then what the argument really boils down to is “I want the maintainers to do and continue to do work in supporting 1.x version bindings so I don’t have to do any work to upgrade.” That isn’t a very compelling argument.
If you do know of a capability that is missing from MQTT 2.5, then please file an issue.
The above poll was created by one of the active developers on OH and there have been replies from several other active developers on the openHAB project. From what I can tell, they are using this poll to prioritize their efforts to make sure that the minimal number of users are impacted with a loss of capability when/if the 1.x compatibility layer is dropped. It is not a goal to ensure that there is no work that needs to be done by users to upgrade their 1.x bindings to 2.x versions. The architecture and how 2.x works is fundamentally different. Of course there is going to be some work.
The best way is to file issues.