If you just install docker using the addon, then disable the addon, then your services/containers, everything works great and no kill messages.
This may mean you don’t get updates to docker/the docker addon, but you can do those manually (if you need to - as it is really just a service runner here, if it is all working, it do you really need updates at all?)
Basically just use the addon to install docker, then remove the kodi side of things and use docker fairly much as normal, works well…have been using it with 19 for a few months now without issues (after I disabled the service part of the addon on).