We use Discord and Roll20. I personally don't like Roll20 but my players seem used to it. I find it too fiddly and the learning curve too great. I also find the Traveller integration harder (it seems optimised for D&D 5th). I'd like to use macros more but even as a old-school software engineer I find the syntax to be difficult to use with Travellers rather fluid skill check system*.
The character sheet system is a bit clunky as you can only have one "document" that has to serve as Character Sheet, Ship Roster, NPC sheet, Creature sheet etc. I did like the token macro system but much of the information I need to generate useful macros is not on the Character Sheet.
Mapping is also harder as you have to specify a custom grid and you have to then scale your map to it. Since combat tends to be infrequent in game (since it is so deadly) producing the map is not really worth the effort most of the time and it is a significant overhead for the GM.
I am not using the online books as I have already paid for them once and fundamentally object to buying them again for a specific platform that I may not use again. I also have to house rule so much that I prefer my players not keep rules lawyering.
Wrestling with the platform in game means we are frequently breaking immersion as I get distracted by either having to write a macro on the fly to cover this weeks unexpected problem solving attempt or try to interpret results while riffling through 3 or 4 digital rule books (too many rules spread over too many books).
However as there is now a free Roll20 Traveller adventure which hopefully has all the key aspects integrated I am looking at it in parallel to see how it does it. So far other than access to an online rulebook, I am not seeing it solve any of the issues I have experienced with Roll20.
We also found Roll 20 frequently unreliable when we used it for D&D as it seems to use a lot of bandwidth. Integrating voice was a bridge too far so we were always running Discord in the background.
Mostly we use Discord now as it allows editing the Chat, we can play offline and it is far more intuitive. We have integrated Dice Roller and as the syntax is no more arcane than Roll20 and I have to hand fettle the rolls anyway it seems less cumbersome.
However it could just be that I miss being round a table and all this used to happen there too, but as we were there in person it didn't seem to matter as much. A comfortable silence in person is sometime welcome, but dead air on radio is verboten.
*or possibly I am just a grumpy old fart and cannot be doing with the faff as much as I used to. I am not as big a fan of Python as the new chaps so maybe I am too much of a dinosaur. Then again we used to test software rather than expect our users to, so what do I know.
