I'll post an update here: I've been contacted by a TP-Link engineer, who provided me with a way to collect debug logs related to the situation. I've tried doing the process as he described, and then...

@Solla-topee one more capture file attached. my home router is a keenetic, at work we're using a bunch of different bridged APs and juniper srx units. no outbound network filtering anywhere. edit -...

@Solla-topee attached a tcpdump capture file of what happens when I try to initiate firmware update using Tapo app from two affected P100 plugs. you can open it in wireshark. and a few screenshots....

@Solla-topee same here with several plugs, stuck at 1.4.3 and fails to update. DNS at 8.8.8.8, no firewall. tried different ISPs, nothing. update just cancels out at "downloading 0%". since this...