If you are using the openbox method, the openbox file is at a different location after 20.04.
If you are upgrading from Lubuntu 20.04 LTS that has LXQt, this new version uses a different Openbox settings configuration file. If you have customized ~/.config/openbox/lxqt-rc.xml you will want to copy that file to ~/.config/openbox/rc.xml.
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