MapTools is the only FOSS virtual table top software I am aware of. It has all the features one would need, extensive dice rolling commands, a shared map and tokens, it even has fog of war options. But out of the box it's very barren. You can download user created libraries and frameworks. Since 5e is very popular there are tons of resources available. And only the host has to download and install them manually, connecting players will download them automatically when joining.
But don't expect it to be as neat and tidy as the paid options. It gets the job done and you can do a ton of stuff with it but it isn't anywhere nearly as intuitive as some of the other tools. Especially the host/gm will need to invest some serious time into the software.
You can find it here https://www.rptools.net/toolbox/maptool/ since it's free just take a look if it's "good enough" for you.