Two controversial issues in one post. Are you going for the record? ;-)
Some people grease, some people use gear oil. Both argue vehemently.
The factory says oil, period. Enthusiast publication in the day actually issued warnings against using grease due to sudden, total trunnion failure. England is a wet land and water gets EVERYWHERE and corrosion follows shortly thereafter. If you are in a dry climate, you may not have the same issue.
Using oil means the trunnion operates in a oil bath. The trunnion has a cap soldered at the bottom to retain oil. It also has a large slot through the thread to help oil spread to all the threads. Therein lies the problem. That same slot allows the fresh grease being pumped in to simply bypass the threads and go straight out past the rubber seal. The old grease is not forced out and simply remains there, drying out and deteriorating.
Again, dry climate, sunny day use, 200 miles a year total (the norm for restored vehicles) there will probably not be any issue at all.
However, if you actually drive your Europa, rain or shine, and put on the miles -- slow year for me, only actually got it out in late August but will still have 5K+ by the time it goes away -- then you need to use oil.