The check problems on the Debian systems are caused by attempts to write to the user library to which all packages get installed before checking (and which now is remounted read-only for checking).
Having package code which is run as part of the checks and attempts to write to the user library violates the CRAN Policy
Packages should not write in the user’s home filespace (including
clipboards), nor anywhere else on the file system apart from the R
session’s temporary directory (or during installation in the location
pointed to by TMPDIR: and such usage should be cleaned up).
Please correct before 2020-01-08 to safely retain your package on CRAN.
I've had the following note from a CRAN maintainer https://cran.r-project.org/web/checks/check_results_retistruct.html
The check problems on the Debian systems are caused by attempts to write to the user library to which all packages get installed before checking (and which now is remounted read-only for checking).
Having package code which is run as part of the checks and attempts to write to the user library violates the CRAN Policy
Please correct before 2020-01-08 to safely retain your package on CRAN.