I find a bug in Darktable 2.6.2, 2.6.1 and 2.6.0 binary available in Solus repository.
The app is unable to fetch Google Photo/Drive folder list and complain about a picasa library failure :
- (darktable:3803): CRITICAL **: 11:09:56.665: picasa_parse_response: assertion '(ret)' failed
I first opened a case @Darktable github and got this response :
Have to compile against an updated Google Photo library. No idea where and how to do it in Solus.