I use current snapshot version with kernel 5.4.69.
from 5.4.65 version, when connected via pppoe to ISP, using 10 to 20 minutes, then automatically disconnect and reconnect, this takes 2 to 3 minutes, making the internet connection frequently interrupted.....
I added manual pppoe setting from tcpdump (Access Concentrator, Service Name, Host-Uniq tag content), but the problem is still so bad.
The connection just runs 5 minutes and reconnect.
Mine was reconnecting every 5 or 10 seconds. I still want to know your router model. Did you make any changes to kernel .config? Make sure it's "CONFIG_PPPOE=m"
Can you enable debug logging in pppd (uncomment the debug option in /etc/ppp/options), and post the pppd debug output from the syslog during a disconnect? Even if it's not the same issue, these logs will shine more light on your issue.
sometime, it was reconnecting after 30 minutes. I using Kansung K190G4N x86 minipc.
I don't see CONFIG_PPPOE on .config file, maybe it is manual.
I have a Xiaomi Router R3P, but it too.