I tried physically removing the 4G modem card from inside the laptop, because there were messages related to it in the output of dmesg from the time when the suspend fails.
Removing the 4G modem card causes suspend to work properly. 12d1:15bb Huawei Technologies Co., Ltd. ME936 LTE/HSDPA+ 4G modem ** Attachment added: "dmesg-output.txt" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1841070/+attachment/5285478/+files/dmesg-output.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1841070 Title: S3 sleep/suspend fails with Linux 4.15.0-58-generic To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1841070/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
