Well, it could also appear under Not new but not yet published, because it was born starting from indications, I gave some time ago (indications later expanded into a nice tutorial by Issabella), but it has been re-shuffled, so I prefer to give to this new-old its own room.
(Also, the topic "Watercolour" is of some interest recently.)

Here the filter:


It makes use of one pattern out of a set I already posted, but for those who didn't download it yet, here it is again:
(you may choose another one inside the set)


It makes also use of one "paper" pattern out of the below set (I guess I posted also this one some time ago...):
(you may choose another one inside the set)



edit: see also the required gradient (MyFGtoBG attached below at post#4)

A sample:


(someone could recall similar outcomes shown when chatting about the tutorial)

Hi there,
the filter does not work in the German version.
The reason for this is the gradient.

German = VG to HG
Englisch = FG to BG

Regards Hardy

Sorry, missed the internally used gradient:


Thanks Hardy for detecting the omission

Beware (for those who like to personalize the filter code):
- do not replace this gradient with the std FGtoBG, because it has been build to generate the typical watercolour effect of borders richer of colour (of course you may create a similar one modifying the mid point)

Just to show the effect of changing the aquarel and paper pattern, by choosing another one from the provided sets.
Source and nr of areas are the same.

...and changing again the paper

Hi there,
Many thanks - everything works perfectly.

Best regards, Hardy

Good!!!!! I love this effect.
Thank you so much Dinasset.

Thank you dinasset for this new filter. We now have something to deal with if we are quarantined ...
great your outcomes, Issabella and dinasset.

Thanks Issabella, I remember you were also loving this effect when talking around the tutorial you wrote for me.
Very nice outcomes, particularly the trees and the roses.

ehehe....

Thanks Dinasset and Level.
Dinasset, you have made that this beautiful effect is so real. I enjoy it and I like to have several possibilities to get the right intensity.

Great !
I couldn't choose among all those excellent outcomes.
Thanks a lot.

dinasset, I just started my tests with the plugin,and with these parameters:



and I had a bug with this message and it crashed Gimp and also Firefox.



I don't dare to start again

I cannot understand that error, it looks like a system error, not an application error.
Can you try to:
- close gimp and all running applications
- shut down the PC and restart it
- restart just only Gimp
- try again to launch that filter

Wow, this is truly a great filter, thank you!

Thank you!
No problems?
Any idea of what can level_0 error mean?

No problems, probably because I'm on Linux.
I don't know, but google says that gspawn-win64-helper.exe is a part of Wireshark program.