
Ingen (^) was the first LV2 host to support CVPort, then Non-Mixer and Non-Timeline followed with JACK CV support for automation. More recently the JACK metadata mechanism enabling CV ports was added to JACK2, and CV support can be found in JACK clients/LV2 hosts Carla (v), Synthpod, Jalv, mod-host and Zrythm, plus hardware support on the MOD Duo X, Poly Beebo/Digit and (soon) Zynthian.

The LV2 format also allows for metadata relating to the min, max and "unit" values for the CVPort. Carla also passes this metadata on to any exposed JACK CV ports, plus Carla allows plug-in parameters to be exposed as CV ports. There is also carla-git / carla-debug-git (better crash information) available in the AUR for Arch (and Manjaro, etc. users).

In JACK:
* https://jackaudio.org/metadata/signal-type
* https://github.com/jackaudio/jack2/blob ... metadata.h
* https://github.com/jackaudio/headers/bl ... metadata.h - jack1
In LV2/Ingen:
* http://lv2plug.in/ns/lv2core/#CVPort
* http://lac.linuxaudio.org/2015/papers/24.pdf - see section 2.4
JACK client/LV2 hosts (* = commits):
* Ingen - original modular LV2 environment *
* Non-Mixer - modular JACK channel strip (LV2 plugin host fork) *
* Jalv - simple yet featureful host that exposes ports to JACK, essentially making any LV2 plugin function as a JACK app *
* mod-host - an LV2 host for JACK, controllable via socket or command-line, used on MOD Devices hardware *
* Carla - graph, rack and single host, JACK/ALSA/PulseAudio *
* Synthpod - in the gap between pure textual (e.g. SuperCollider) and pure visual flow (e.g. Pure Data) audio programming paradigms *
* Zrythm - a new DAW focused on electronic music production *
* GStreamer - library for constructing graphs of media-handling components *
* Spaghettis - Pure Data fork with metadata support *
Plugin bundles and suites with CVPort support:
* ams-lv2 - port of the AlsaModularSynth (AMS) internal modules to LV2 (archived older version; avw.lv2)
* blop-lv2 - generators, filters, and various utility plugins
* fomp - 1 auto-wah, 1 EQ, 3 chorus, 2 phasers, 5 filters, 3 oscillators, and 2 reverbs
* vcf-lv2 - filters: two low pass, a high pass, two band pass, notch, peaking EQ, low shelf, high shelf
* ZLFO - multi waveform oscillator, comes with Zrythm
* infamousPlugins - envelope follower & stop/start effects
* beatslash-lv2 - beat repeater & beat slicer
* vm.lv2 - programmable stack-based virtual machine
* mephisto.lv2 - a Just-in-Time FAUST compiler embedded in an LV2 plugin
* mod-cv-plugins - a multitude of handy utility bundles
* cv-lfo-blender-lv2 - 4 synced LFOs with blended output, made using DPF
* arpeggiator_LV2 - an arpeggiator and a MIDI-pattern plugin
* non-zyn-CV - automate zynaddsubfx using non-timeline CV automation via synthpod
* uhhyou.lv2 - various filters, oscillators, slew limiters, envelopes
* cv_to_cc.lv2 - translate CV to MIDI CC
* audio-to-cv-pitch-lv2 - converts audio to CV pitch (1 volt per Octave)
* lenticular.lv2 - port of MI modules to LV2
* PolyLV2 - a collection of LV2 plugins designed for modular / eurorack style use.

Conversion/testing:
* mod-spi2jack - JACK client for converting SPI to a JACK control-voltage stream and vice-versa
* midimsg-lv2 - basic MIDI aftertouch, CC and mod wheel to CV
* MIDIMonster - Multi-protocol translation software (ArtNet, MIDI, OSC, ...)
* mod-fake-control-voltage - A small Jack-internal client to simulate the physical CV-ports
* jm2cv - older, doesn't use JACK metadata
* jack_property(1) - JACK client to list, set and delete metadata information
Frameworks supporting CV ports:
* DPF (template)
Basic sequencing is possible from MIDI (via mod-midi-to-cv-mono, mod-midi-to-cv-poly, midi2cv of Carla, Note of Ingen, or MIDIMonster), or by using Non-Timeline. Possibly a more advanced UX might come first from a project like Zrythm, Radium, ossia score, QMidiArp or Element.
More info on the MOD plugins here, here and here, with discussion on the MOD forums. More on Zynthian here, and the POLY pedals here.
VCV uses -1..+1 (evenly distributed 24bit, no exponent). MOD uses 0..10 or -5..+5 Volts directly, also for internal signals. Since the default is 10V peak-to-peak, a conversion is easy to handle; 0.1 .. 0.2 <> 1 to 2V. LV2 does in theory allow min/max range for CV ports, but anything other than -1..+1 or 0..+1 for unipolar doesn't make much sense.
Extra notes:
* Hardware compatibility requires a DC-coupled device audio interface. The MOD Duo X is DC-coupled, but the original MOD Duo and the MOD Dwarf are not.
* Hardware DACs and ADCs vary, the MOD Duo X DAC and ADC are 12-bit. See also Choosing a DAC for Control Voltages.
* VCV doesn't have JACK CV support, and skjack-vcv is currently undeveloped. Edit: a solution is on the horizon
* See also Bigwig Studio CV and Ableton CV Tools?
P.S. N.b. I was compiling things on this GitHub issue before making this post, and I have heavily copyedited the above as things have changed.
Edit: LV2/JACK Modular - Facebook group