If I do gphotosdl -login, I'm able to successfully log in.
However, if I subsequently do gphotosdl, I receive the following output:
2025/06/25 14:12:08 INFO Please log in, or re-run with -login flag
2025/06/25 14:12:09 INFO Please log in, or re-run with -login flag
2025/06/25 14:12:10 INFO Please log in, or re-run with -login flag
(...)
If I do gphotosdl -show, I can see that my account is still known, but that it has been logged out. If I try to log in again, I get a message "This browser or app may not be secure." Same as discussed/shown here: #10 (comment)