How to override all RVT links in all view templates to display as half tone?

Hi @louisbanks and welcome

you need to get all RevitLinkType and use SetElementOverride (instead of by Category)

see an example here

if you haven’t done so already, take time to read the forum rules (How to get help on the Dynamo forums ) and the community guidelines (https://forum.dynamobim.com/faq )