I have see this message, "failed to update metadata for lvfs" a couple times now when checking for a software update. It doesn't happen often but running the following command seems to help.

Distribution upgrade worked for me.

I am running a Librem14 (5.10.0-9-amd64) and was experiencing this same issue. Instead of purging gufw I needed to purge ufw. Before purging I noticed the ufw service was in a masked state after removing the package with apt. I also cleaned up /etc/ufw after the purge. I used the iptables rules in this bug report as a workaround and saved those to /etc/iptables/rule.v4 and .v6 so iptables-persistent would see them and rebooted. This fixed my issue, the networking was restored and the machine no longer would hang after decrypting the drive.