I haven't tried there standalone fx, but if their built in synth fx are any indicator, you should be able to get some nice sounds from the standalone fx. I do feel like Uhe fx tend to be a little more opaque in terms of the names and values. E.g. having a filter that goes from 0 - 100 instead of just putting the cutoff frequency is a bit too old school. Having a parameter on a delay that's just called "wow" is not very helpful.
In any case all of these companies support Linux, and they all produce software worth taking a look at.
https://www.kvraudio.com/marketplace/linux/new-to-kvr-market...
There are whole little communities that do, but you have to dig for 'em. I recently joined Unfa's patreon (reviewer and popularizer of OSS and Linux music-making gear) and joined his discord server. Only to discover they had an emote of my face, due to my OSS plugin making and because they liked my catchphrase 'I'm Chris from Airwindows and hey… you can do this!'
And so you can. The stuff is out there, and if you look around it's absurd what you can do. My favorite discoveries lately are Bespoke, and the Surge Synth ecosystem (hugely impressive and helpful to other OSS projects of all types)
But you'll find it's a bit of a media freeze-out as far as people TELLING you any of this is happening. I can attest that if you do compile your stuff for Linux, you'll hear almost nothing about it, including from the folks you are supporting. I've got a Mediafire mirror for my stuff that tracks downloads across all my updates. Signed MacOSX bundle supporting M1 machines, 3023 downloads. LinuxVST, 325 downloads.
You do Linux support because you care about it as a concept, not because you're going to get any benefit from it. It doesn't pay, it costs (in dev time that won't be compensated, any more than if you were developing one of the little libraries upon which all the Internet depends). You have to have other work lined up to support you while you do the added Linux support.
I buy music and other software to use on Linux all the time. A few individuals willing to play for software might not be significant but I just signed up with your Patreon so hopefully now you're at least partially incentivised to keep releasing your plugins on Linux.
The question is more whether I'll be compelled to stop work because I'm NOT surviving, but so long as I am, my incentive to release plugins on Linux is because it's the right thing to do. Also, I think it matters to have stuff out there where the barrier to entry is ability and education, not capital. I think basing everything off only how much capital you start with and are able to exploit, distorts things in very unpleasant ways.
Fortunately, so long as I'm alive and have internet I'm able to do something about it. Maybe, so can you! :D
It's worth thinking about why this is. I am very determined to stick with the kind of messaging and attitude that I like. I also have a strong intuitive feeling that it's not a good match to what platforms and competition and basically internet capitalism want to see out of me, and they've got enormous pressure to bring to bear, and many ways to direct me towards becoming what's useful to them, and indeed punish me for not doing so.
That would mean that if it's in any way hard to find 'that attitude' you're appreciating, it's because it is reserved for people who both have it and are willing to take a beating to keep it. As we think about stuff like that, think about what ways platforms would like you to be more, I dunno, Logan Paul or PewDiePie etc in nature, for engagement, and in what ways they're able to deliver pressure and advocate for those on their platform to take on that form.
https://github.com/ValdemarOrn/CloudSeed
I guess it can be compiled for Linux with some kung fu build skills. I ported it over to Electrosmith Daisy STM32, which is very cool too: https://www.electro-smith.com/daisy
But if you don't want the hassle, look at the Effects that it already has onboard - maybe Valhalla VST's aren't that necessary, anyway:
https://wiki.zynthian.org/index.php/Zynthian_Supported_Synth...