I solved this myself so am posting for the benefit of others.
I found that with a particular news aggregator site, none of the main story external links would work. Mousing over them showed the URL but nothing happened when clicking.
Other internal links on the site worked fine.
hhhmmm...strange...
Firefox opened the site fine, so I spoofed FF, and Chrome and Edge, but to no avail.
I went through the source code but didn't spot anything.
I saved the site locally, opened it and the links all worked!
So I started going through settings and found the culprit - block ads on abusive sites.
Now, this isn't an abusive site but whatever...

I found that with a particular news aggregator site, none of the main story external links would work. Mousing over them showed the URL but nothing happened when clicking.
Other internal links on the site worked fine.
hhhmmm...strange...
Firefox opened the site fine, so I spoofed FF, and Chrome and Edge, but to no avail.
I went through the source code but didn't spot anything.
I saved the site locally, opened it and the links all worked!
So I started going through settings and found the culprit - block ads on abusive sites.
Now, this isn't an abusive site but whatever...

My Computer
System One
-
- OS
- Windows 11 Pro 24H2
- Computer type
- Laptop
- Manufacturer/Model
- LG
- CPU
- i7 Ultra
- Memory
- 16GB
- Graphics Card(s)
- Intel
- Sound Card
- Intel Realtek
- Monitor(s) Displays
- Laptop 17" & TB4 Dell 27" QHD Ultrasharp w/integral TB4 hub
- Screen Resolution
- 2560x1600
- Hard Drives
- 1TB SSD, 5 external WDs
- Mouse
- Logitech Master MX 3S
- Browser
- Vivaldi
- Antivirus
- Kaspersky Premium Suite