x42 LV2 instrument plugins not working on Linux

First, this is an amazing app, thank you for making it available! I'd really like to use it as a replacement for falkTX's Carla in my computer music courses at the JGU, but I'm running into some issues with the LV2 plugin support, which I'm reporting here.

This is on Manjaro Linux, using the Element stand-alone, Element built from the latest gitlab source (reporting itself as 1.0.0-1cfa4191 build 175). Most LV2 plugins work fine, but I'm getting some issues with x42's (Robin Gareus') instrument plugins from https://x42-plugins.com/x42/midi which I use a lot.

Specifically, plugins like General MIDI Synth, which load samples during startup, fail to properly initialize. Afterwards, Element just hangs and I need to kill it. Short screencast demonstrating the issue:

I have exactly the same issue with the AVL Drumkit plugins such as Black Pearl Drumkit. Both plugins work fine in Ardour.

Also, the setBFree tonewheel organ plugin looses some or all of its built-in programs in Element. Here's how setBFree's Recall PGM page looks like in Ardour:

This plugin can be instantiated in Element, but its program menu is only partially populated:

(BTW, in the 0.46.6 AppImage, this menu comes up totally empty.)

So maybe there's something missing in the LV2 initialization sequence? At least the gmsynth and AVL drumkit plugins seem to point into that direction.

Also, this is probably unrelated, but what's up with the MIDI ports suddenly being red in the current git version? That also seems to impact functionality. E.g., here's how the Dexed LV2 (https://asb2m10.github.io/dexed/) looks like in 0.46.6:

Setting the MIDI channel filter on the MIDI pane also works alright.

On the latest git version, it looks like this:

And it seems that the MIDI channel setting on the plugin just seems to be ignored; the plugin appears to be in omni mode all the time. Is that intentional? Could it be changed back to the behavior it had in 0.46.6?