I know this thread hasn’t been touched in a hot minute, but I remember first seeing WoltLab back when they had their “Lite” free forum offering with limited features. I thought it was good, but then being primarily German focused left a huge gap when it came to support.
However the past year, with their free CMS (article system, page system, etc.) and their whole move to new features (gallery/blog/calendar/cloud solution), it boosted them to be seriously considered. Like any paid software, not many things are for free (styles/plug-ins), but their support speaks fluent English, their community also is pretty full of English speakers who are willing to help, and their documentation is extremely detailed (enough to where you could even dive in and make a plug-in yourself).
I’ve had a license with them for the past 2 years, but ever since early 2019 is when I have given them another shot and wasn’t let down for the price.