LinuxMusicians

I still get a hang after clicking 2 or 3 times on the helm LV2 Show GUI option still. Also, I'm getting a strange double entry thing going on now and I didn't have this a few days ago when I last built from git. I'm using Archlinux on Wayland, but the same thing happens on Xorg.
Below I have attached a file with my results plus some relevant images to help. I did this output test only after manually deleting the scanner folder and its contents.

These fixes were for the scanner auto-rescan problem thingy, not for Helm.

As I type, I am building Helm...

Yes, it is taking that long, 15 minutes now ...
Whoa, this thing must be real beast...

[Edit:] And... 15 minutes later it's still building. Ho hum... Time... for... a... coffee...

I also find it weird how I'm now getting two entries for all Linux native vsts, but not for my LinVST bridged ones. It didn't do that a few days ago. Not a functional thing just it makes the menus a bit more annoying now.

I'm getting a strange double entry...

Observed. Sorry about that. Was simple neglect to store LinuxVST plugin name as well as label.
Fixed in git master now.

After pulling the fix, please force a rescan either with the -R command line switch or
via Settings > Global Settings > Plugin Paths > Force Rescan.
(The caches need to be rebuilt to newly store the LinuxVST plugin names.)
That should finally make the double entries go away.

Were you able to test and compile Helm LV2?

Yes. Observed the issue.

Still checking.
Not sure if I'll have a fix soon, this one is tough.
Hang in there.

ATM I'm trying to understand why we are not receiving ANY UI midi events from LV2 plugins.
The mechanism is there, it is connected, and... nothing.
I need to get this working because AVL DrumKits LV2 is not working AT ALL. You hit the drums and... nothing. Not even the visual 'hits' effects.
And... Helm's ui does in fact open, once or twice before crashing, but no sound from midi tracks, no visual events...
Same with Zyn. It has a UI midi out port but we're not getting anything.
I'm not exactly sure when we're supposed to get these midi events.
Checking...

I can confirm that the AVL Drums don't show their purplely red animation either like in Ardour. Weird. However a workaround, for now, is I can play them in the drum/piano roll in Muse and they sound fine. Thanks for fixing the scanner bug.

Huh? Wow I can't get anything out of AVL drums.
Not even from the pianoroll/drum editor.
I've tried hitting all notes or drum notes. Nothing.

How did you achieve this?

[Edit:] Can you tell me which version of AVL DrumKits LV2 you have? Thanks.

I add an LV2 synth --> Black Pearl Drums (NOT The Multi-Output Variant) to Muse's arranger view. Next, I add a midi track and create a clip on the arranger's timeline. then I open a piano roll view and use the pointer tool and click on a note. It works the same way but instead creating a drum track. Also, I have set in my settings to use the new style drums which is the default.
The AVL Drums version is 0.3.1 from Archlinux.

Other problematic plugin versions as you mentioned are:
helm = 0.9.0
zyn-fusion = 3.0.3

That's what I tested with. Lastly, I'm using your latest git (master branch) for the tests.

OK Thanks. Hm, just installed the latest AVL DrumKits from git.
No change

Also, I have set in my settings to use the new style drums which is the default.

Oh, the so-called 'new drums' vs. 'old-drums' is gone now. They were merged into just one 'drums'.
What you see there in Settings is a relic that needs to be removed.
The setting is ignored internally. (Or at least hopefully should be).

Works with Jack Audio. You might need to change the midi port to the Black Pearl Drumkit LV2 as well at least when I compiled Muse on Archlinux it defaults to the first available synth. It should work on other backends using RTAudio, but I have not tried switching them yet.

Try building your Muse software with libinstpatch support and my build also has no lash support built into it as well. This should be the only difference between my build and the default Muse build on Ubuntu. It may be a very remote chance that your version of mesa or libinput may have an issue if you're building it with the latest qt 5.12 on an Ubuntu LTS, I had a similar issue a while back in Ubuntu 16.04 after compiling Qtractor and not being able to get sound out of certain plugins when using qt 5.9.

I reached out to AVLD's issue page for help. Wait and see.
I tried everything.
So now there may be an indication that it is system related ie. yours vs. mine. (opensuse Tumbleweed here. Cutting-edge daily builds.)

Hmmm. last I tried tumbleweed it ended with dependency hell, I'd rather develop against Fedora's Rawhide. Still works here on Arch and I tried all the kits including multi-out. Whoops, I forgot to give you these two package versions that may help more.

lilv = 0.24.4
lv2 = 1.16.0

Archlinux rolls both runtime binaries and development libraries into a single package. This is all I can think of that may be different and/or causing you headaches.

I recall having trouble a few years back that I could not get any sound out of certain kits in AVL (cannot remember which). If I'm not mistaken it was intermittently working for one of the kits, which I used in a song, sometimes had to restart a few times before it made any noise.

Slightly OT but I'll say that the only reason I switched to suse was because of the KDE Breeze and Oxygen fiasco
with MDI windows that totally froze MusE and took me months to figure out and when I did, they were very kind in fixing it
but I'm sitting there with KUbuntu LTS waiting like everyone else for a long awaited new release.
So Tumbleweed is perfect for me. I 'tuned in', and like within days a fix came down the line. Cool.