Thank you @michaelsoetaert. This now merged and it will be released with next version.
I've merged that patch to the 3.x branch. It will be available in the next release. Thank you @plach
https://git.drupalcode.org/project/popup_message/-/merge_requests/19 - I've merged this patch to the repo. It will be available in next release - 3.0.3.
https://git.drupalcode.org/project/popup_message/-/merge_requests/18/diffs - phpstan and phpcs fixes for the module
Created and merged branch for this issue. Thank you @michaelsoetaert.
New released 3.0.2 version is now compatible with D11
rafal.tokarski → made their first commit to this issue’s fork.