I do consider this as a bug, since snapd, based on good effort, but shortsighted security design, blocks access to everything residing in the home directory starting with a dot (i.e. all "hidden" files and directories), while thunderbird seems to permanently read ~/.xsession-errors.
The security measures of snapd don't seem to allow thunderbird to run in every details, and this looks like a bug.
I do consider this as a bug, since snapd, based on good effort, but shortsighted security design, blocks access to everything residing in the home directory starting with a dot (i.e. all "hidden" files and directories), while thunderbird seems to permanently read ~/.xsession-errors.
The security measures of snapd don't seem to allow thunderbird to run in every details, and this looks like a bug.