apt install linux-image-4.4.0-22-generic=4.4.0-22.39 linux-image-extra-4.4.0-22-generic=4.4.0-22.39
should downgrade those and make apt happy, then you can install -23.40~bpo1 from the url without worries, and that'll upgrade to proper -23.40 once it's available, or you can purge them after testing
apt install linux-image- 4.4.0-22- generic= 4.4.0-22. 39 linux-image- extra-4. 4.0-22- generic= 4.4.0-22. 39
should downgrade those and make apt happy, then you can install -23.40~bpo1 from the url without worries, and that'll upgrade to proper -23.40 once it's available, or you can purge them after testing