Foundry is outstanding. My groups moved to it after being frustrated with Fantasy Grounds and Roll20. Only parts of it are open-source, but I don't mind in this case. It can be self-hosted, only one copy is needed, the price is reasonable, and the money goes to a small team of independent developers rather than a big corp.
(My one notable criticism of Foundry is that their official support community is on Discord, which I won't use. This hasn't kept me from using the software, though. There are plenty of other users out there, so it's pretty easy to find information when I need it.)
We use Mumble for voice chat. Open-source, lightweight, cross-platform, low latency, good noise filtering (RNNoise), great sound quality. You can self-host, or pay for a super-cheap hosted server.
I remember Owlbear Rodeo being mentioned from time to time a few years ago, but I didn't keep track of it. Wasn't it originally free? Did it go commercial?
@Shkshkshk@dnd Foundry is great, the feats are marvellous but the learning curve is steep in the beginning (loads of youtube videos explaining how to get ready if you are curious). Bright side is you only pay once and all the updates are included
It's also self-hosted, which is great. You're not beholden to yet another cloud service. The other players of your group just connect to your server with their web browsers, so no extra licensing required for them.
If you don't want to, or can't self-host, there is The Forge, which offers a hosted Foundry service, but I don't know what the costs are as I've never used it.
I'm aware of http://fari.app which is FOSS. That's the one I've had my eye on to try.
I've also used a much much older and also free MapTool from http://rptools.net ; the quality there is perfectly fine on the functional end but lower on the aesthetics.