Upgrade 2.3.0 to 2.4.0 MQTT Binding stopped working

I upgraded manually from 2.3.0 openhabian to 2.4.0 running as a docker container.

I now have problems with the MQTT binding.
I have enabled debugging

log:set TRACE org.openhab.io.transport.mqtt
log:set TRACE org.openhab.binding.mqtt

I did all sort of actions: uninstall install binding, changed the mqtt.cfg.
I do not see any trace in the log file, neither do my items do any traceable output:

Number CWLStep0Vol  "CWL Volume 0  [%.0f m3]"       (gPersist)   {mqtt="<[mqtt:ebusd/wolfcwl/LuftmengeStufe0:state:default],>[mqtt:ebusd/wolfcwl/LuftmengeStufe0/set:command:*:default]"}
Number CWLStep1Vol  "CWL Volume 1  [%.0f m3]"       (gPersist)   {mqtt="<[mqtt:ebusd/wolfcwl/LuftmengeStufe1:state:default],>[mqtt:ebusd/wolfcwl/LuftmengeStufe1/set:command:*:default]"}
Number CWLStep2Vol  "CWL Volume 2  [%.0f m3]"       (gPersist)   {mqtt="<[mqtt:ebusd/wolfcwl/LuftmengeStufe2:state:default],>[mqtt:ebusd/wolfcwl/LuftmengeStufe2/set:command:*:default]"}
Number CWLStep3Vol  "CWL Volume 3  [%.0f m3]"       (gPersist)   {mqtt="<[mqtt:ebusd/wolfcwl/LuftmengeStufe3:state:default],>[mqtt:ebusd/wolfcwl/LuftmengeStufe3/set:command:*:default]"}
Number CWLBypassOp  "CWL Bypass Operation  [%s]"    (gPersist)   {mqtt="<[mqtt:ebusd/wolfcwl/Bypassbetrieb:state:default],>[mqtt:ebusd/wolfcwl/Bypassbetrieb/set:command:*:default]"}

use to work in 2.3.0.

Here the the only mqtt.cg entry:

# URL to the MQTT broker, e.g. tcp://localhost:1883 or ssl://localhost:8883

Did test at console, which works perfect (mqtt broker ok)

mosquitto_pub -h vevedock -t 'ebusd/wolfcwl/LuftmengeStufe1/set' -m '75'

I am out of any further ideas!

Please have a look at paper ui and check if the mqtt binding (OH1 Version) is installed.

I guess your update introduced the ability to install the openHAB 2 mqtt binding, which automatically makes your used OH1 version “legacy” and uninstalls it.

If it isnt installed and you cant find it under addons, you have to enable legacy bindings.

After that you should be able to install the oh1 version and everything should work again.

Info aside:
You can check the installed binding version on console with:
bundle:list -s | grep "mqtt"

I do not see OH1 mqtt binding in paper UI

here the client output:

openhab> bundle:list | grep -i mqt
285 │ Active   │  80 │ 1.2.0                  │ Paho MQTT Client
287 │ Active   │  80 │ 0.10.0.oh240           │ Eclipse SmartHome MQTT Binding
288 │ Active   │  80 │ 0.10.0.oh240           │ Eclipse SmartHome MQTT Thing Binding
289 │ Active   │  80 │ 0.10.0.oh240           │ Eclipse SmartHome MQTT Transport Bundle

Take a look at my second screenshot.
You should be able to see and install it after enabling the legacy support.
Or did you activate it already?

Why should I use the oh1 version

ok see have to read through documentation, sorry

The OH1 and OH2 bindings are highly different in the backround and in their usage.
So you need to migrate your mqtt devices which will take some time maybe.

For sure it would be better to use the new one on long term, but the old version is simply not compatible to the OH2 version.

WIth using the OH1 version (for now) you should get back your full functionality very fast and are able to migrate step by step afterwards without a need to rush.