I had the same problem as the rest of you after the latest update, but with some serious headscratching I tracked it down to Intego NetBarrier and I found that by turning the firewall protection OFF everything was back to normal without the need for any re-intallations of any software. I then contacted Intego and they informed me about 3 hours ago that they are aware of this issue and that they are working on a fix. They confirmed that disabling NetBarrier was the short term solution until they fix it. Hope this helps you all and perhaps switching OFF any type of firewall that you may have running will solve the issue for even more people.
I had an email late last night from Intego informing me that they have released an update to NetBarrier (v 10.9.9) and that this should fix the issue. Initially when I installed it and switch the Protection back ON all looked fine and I was back surfing at full speed. This morning I opened NetBarrier to discover that all my previous rules have disappeared and that there is no way to add rules or revert to my original set because that pane is showing Disabled. So this is not a fix from Intego, it is a way to buy them more time to sort it out properly. I emailed them again asking WTF but so far I have not had a reply. In conclusion, this means that NetBarrier is currently NOT protecting me/you and is as much use as the proverbial chocolate fireguard (pun intended). I will post again should Intego reply to my query.
Here is the latest reply as of 12:00 - 31/10/2019 from Intego regarding this issue.
Dear Intego Customer,
As a first step after 10.15.1 update issue, our development team worked to circumscribe the network connections slowdowns. They achieved this by temporarily disabling the application rules, which is the component in conflict with 10.15.1.
That's why the right pane of Applications tab is disabled
As you may notice NetBarrier firewall is still active.
We sincerely apologize for this situation, and thank you for your patience while we work to restore full protection.
Sincerely,
The Intego European Support Team.
Not quite out of the woods yet folks, watch this space......