Here is some handy stuff for using VTT's with GURPS
Mook's VTT Review Detailed and includes notes and links to third party or fan created content.
Fantasy Grounds Unity
The GM can purchase a standard or ultimate license and depending on that players can join with a free demo license or purchase a standard license.
Cost: $39 Standard or $149 Ultimate (12/2020)
This is a purchasable application and its hosted from your computer. This may require more technical expertise by the GM to set up the hosting and work with the security settings. Also it requires a good internet connection and bandwidth from the GM.
Cost: $50 (12/2020)
- Foundry Virtual Tabletop
- Mooks Youtube video It shows one module add on that works with GURPS Character Assistant and your purchased PDFs.
- Foundry Discord Server
Popular and free to play, though GMs can purchase more for extra features. Its hosted on servers not your computer so easier for less technically inclined GMs.
Cost: Typically free to use but there are addons and extra options you can purchase.
The ones above seem to be the major contenders. Here are a few more and any feedback is welcome.
Discord is a popular system for voice or text communication, even vide though it can be laggy. I prefer it as the group can communicate between games and leave messages for each other.
Google Hangouts is another option but is being discontinued soon.
Zoom, Skype, etc are also used by some.