Roll 20 has, iirc, the benefit of being designed for the exact task. Never used it, but I think it has all manner of RP helpful stuff built in. Integrated character sheets, map support, etc.
Looking at
this quick guide it looks like it supports voice OR text chat, which could be a plus if we can all figure out one of the two options.
Looks like if we are going that route, whoever is running a game will need to swot up on the app itself, but it does have a lot going for it in terms of features.
Discord I'm passingly familiar with, but it's got little to recommend it beyond being a serviceable text chat thingy. I think it has some kind of voice capabilities as well, but I've never even considered trying them out. It's a step up from the old IRC clients in the sense that it's persistent and the chat itself doesn't go away I guess, but you'd be doing everything else off-app.
Video chat is no benefit to me, as I don't have a camera for that. I mean, I may be having to improvise a little even if we go
audio, but I have options that
should work for that if necessary.
EDIT - If it comes to it, do we have enough of us with some way to do voice chat? That solution requires hardware. I'm hoping I can get my gaming headset working with the desktop, as I've done so before with an older and crappier one. What about the rest of you? Text is a good fall-back option, but it's a lot slower even if you are used to typing a fair bit.