assinaturas inválidas EXPKEYSIG

desculpe se fiz algo idiota, mas eu realmente aprecio alguma ajuda.

isso aparece sempre que tento verificar se há atualizações

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://download.opensuse.org/repositories/home:/strycore/xUbuntu_18.04  Release: The following signatures were invalid: EXPKEYSIG 2F7F0DA5FD5B64B9 home:strycore OBS Project <home:strycore@build.opensuse.org>
W: Failed to fetch http://download.opensuse.org/repositories/home:/strycore/xUbuntu_18.04/Release.gpg  The following signatures were invalid: EXPKEYSIG 2F7F0DA5FD5B64B9 home:strycore OBS Project <home:strycore@build.opensuse.org>

Você precisa visitar a página do repositório e adicionar novamente a chave de assinatura do repositório:

wget -nv https://download.opensuse.org/repositories/home:strycore/xUbuntu_18.04/Release.key -O Release.key
sudo apt-key add - < Release.key
sudo apt-get update