Near zero upload speeds since update to Sequoia 15.1.1

I have full fibre 900mb u/d speed broadband connection.

I am using Macbook pro 2018, recently received an upgrade( couple of weeks back ), which took me to Sequoia 15.1.1.

Since then I have seen my upload speed dropping drastically to near zero (Both wired and wireless ), only on my Macbook pro. All other devices ( Android phone, tablet, windows laptop and 2015 Mac mini ) are consistently getting upload speeds of over 300mbps.

But upload speeds on my Mac is almost zero, to the extent that I am not even able to send emails.

Everything was fine prior to this upgrade, with the same broadband provider. There has been no change in any router settings.

I tried both wired and wireless connection but it's the same problem.

Apart from that so far I have tried following things but nothing has helped to fix the issue.

1) Swap ISP router with my own router

2) Change wifi connection setting of Private wifi address from rotating to fixed and off

3) Changed wifi connection setting of Configure IPV6 from Auto to manually and off

4) Reboot multiple times (Laptop and Router)

5) Clear browser cache / history

6) Use different browsers (Chrome, Firefox, Safari )

That fact that it is only my Macbook having this issue, I am led to believe this linked to recent upgrade.

Anyone experienced similar issue or have any suggestion how to fix it?

[Edited by Moderator]