OK, I had another look at this. The package I refered to is the one you want, is it? But it doesn't work, whatever you do? At least that was my experience when I just gave it a try.
The reason is plain simple: The Equalizer 'installs' a new output device, and even sets it as default. However, Pulse remembers 'prefered' output devices based on application, so my music player just used the direct output.
Right-click the volume control in the panel, and click on the 'Audio Volume Settings'. Start your player, it should show up in the 'Application' Tab. There's a pulldown menu on the right, open it and select the 'LADSPA ...' output, and the equalizer will work.
At least it does for me
Well, well, well... it's now 3:20AM for me, but i just couldn't go to bed until i sussed this out, & happily now i have, at long last. I'm immensely grateful for your kind help -- vielen danke! Much of what you wrote i already knew, & had already done, but you definitely set me off in the right direction... as i followed through your steps in real-time, to ensure i wasn't overlooking/skipping something, i stumbled onto THE fault, although i do not know if the blame goes to the EQ, or to TW. Whatever, now that i know of the fault, i can simply work around it from now on. It's a huge relief to me, coz not only does it mean i do not have to return Lappy to Maui [yippee], but... i can now also confidently migrate my Tower to OSS FW once i have the time.
FYI, here's what i discovered. Oh, before that, i need to clarify my earlier grumbles about the EQ when i said it didn't work. It always did launch, always did let me operate the sliders, always did let me create & save custom profiles or select existing ones... it's just that the actual sound output from Lappy's speakers always still came from the normal audio device, not the EQ device. Here's why:
I ensured that all 6 items in "Audio Playback" correctly prioritised the EQ not the std device, eg:
I superimposed the EQ atop the System Settings Audio Volume window whilst streaming a Netflix movie in Vivaldi [of course], so that i could watch everything at once. To my surprise [& exactly as you had advised me - thanks again!], despite my defaults in #1 above, initially my marked button below did NOT show the EQ, but was still showing the std device. I had never checked this before, as it never occurred to me that my defaults in #1 above would be ignored. In the pic below, it only shows the EQ specifically coz i manually changed it before taking the screenshot. The instant i made that change, to my delight, for the first time in OSS TW, i was hearing the EQ output. Wow.
However, every single time i made ANY change to the EQ settings, instantly [& THIS is the fault] the output jumped back to the std device not the EQ, eg:
So now that i finally get to see what the damn thing was doing, the workaround whilst inelegant, is simple... plan ahead prior to starting my music / videos by getting the EQ Presets just how i want them & then do NOT touch them again, &/or do this IF i forget what i just said & accidentally do fiddle with the EQ --> bring up the tray popup, click the EQ icon on the RHS, observe the FALSE indication that it's already Default [yes it was, until i disturbed the EQ, when the std device kicked in again], click on the Default box anyway... & instantly the EQ takes over again:
IMO it really should not misbehave like this, but hey, so what, with your great help i now have a totally viable arrangement. Yay.
Oh dear, 3:55AM... Sleep.