there are other packages that can connect to an icecast server
I know these can work with caster.fm streams: * Internet DJ Console (requires JACK) * BUTT - Broadcast Using This Tool * Darksnow
install pasystray
to check pulseaudio default sink and source
most other audio controls only show fallbacks not defaults
for streaming you need to run JACK to create and route multiple mixes
JACK is not like virtual cables; it has a patchbay to connect everything
best to use a JACK controller like cadence to start JACK and sort out connections from Pulseaudio and ALSA
once JACK is running can add OBS, effects and a mixer
the closest equivalent to voicemeeter is probably jack_mixer
but it is not available on some distributions now
i used Internet DJ Console for a few years streaming audio
that has built-in routing for microphones and VOIP callers
it is a little bit like SAM Broadcaster on Windows
that could do most of the audio work in JACK and send audio mix to OBS
suggest you check out AVLinux and Ubuntu Studio that are pre-configured for JACK
the manuals for both of those distributions are good reference information even if not using the distribution
I do live icecast streaming audio with IDJC Internet DJ Controller
Mixx if you want DJ tools
OBS for videocasting
For editing Audacity is plenty good enough on Linux and same as on Windows
Audacity is great for multitrack recording, but not really necessary for podcast editing
Most important package IMO is to get JACK audio server running alongside Pulseaudio
JACK is required for most of the good pro-level audio packages
closest equivalent to voicemeeter for a simple mixer is probably jack_mixer
but there are others like non-mixer if you want more features
If you managed to work out how to connect voicemeeter in windows, you should be able to work out how to do similar in JACK ok