dasp VS vst3sdk

I'd say that interoperability with dasp could be considered here. It supports no_std environment, however looks like it supports only slices rather than proper audio buffers

There is Dasp which seems healthy (focusses on audio) and Basic_dsp which looks more like what I am looking for and which also seems maintained, but I am not sure if it is currently actually developed because the last updates seem to focus on dependency updates and documentation.

But you don't have only Linux, you have (and probably first) OSX and/or Windows and then Linux, and you need an API that works well in that case. Being an in-process dll/so plugin, while fraught with perils gets you to avoid other issues (state, health, restart, identity, etc.)

Also sometimes you don't have a choice, but have to make a dll, for example:

https://github.com/steinbergmedia/vst3sdk or https://ae-plugins.docsforadobe.dev/ and many others. Sometimes it's the only viable choice.

(I wish most have used grpc/flatbuffers/whatever to communicate, but then every RPC call have to be checked/retried/handled, and or shared memory well handled, with (?) locks, etc. - not a trivial thing for someone who is deeply specialized in making a very good effect/renderer/etc instead of dealing with this extra complexity on top).

Yeah, you can use nordaudio which wraps PortAudio which has support for every major audio back-end. As for writing a VST you may have to find a way to wrap or interface with Steinberg's SDK. MIDI support is possible by using an RtMIDI wrapper, which I haven't linked because there are a few of them out there of varying quality and I don't know which is best because I just use ALSA directly for my purposes.

You can read the VST3 SDK manual for yourself here https://steinbergmedia.github.io/vst3\_doc/vstsdk/index.html and access the source here: https://github.com/steinbergmedia/vst3sdk.

You have to use the steinberger SDK to make a vst

https://github.com/steinbergmedia/vst3sdk

But audio plugins come in many formats.

https://github.com/steinbergmedia/vst3sdk#build-the-examples-on-linux

You can do VST3 as GPL. They dual license it. Lots of legalese to read but definitely an option. https://github.com/steinbergmedia/vst3sdk/issues