The copyright dates were outdated in the About dialog in the application. Remove them from this dialog and just put a link to a "COPYING" file at the root of the Electrum ABC subrepository. Don't put any date ranges in the copyright notices, as these are unlikely to be maintained on a regular basis. See https://www.linuxfoundation.org/blog/blog/copyright-notices-in-open-source-software-projects
Rename the "LICENSE" file "COPYING" and add the copyright information, to mirror what is done in for the node software.