How popular is large format photography in Europe?
If you are asking about "amateur" photographers, LF is steadily rising in popularity in Europe/UK.
When I started using LF for work in 1977 it was a specialist format used by Advertising and Commercial photographers, as well as for Applied uses. A few students on art photography courses, like Trent & Derby, began using LF in the early 1980s and specialist stores like Teamwork & Robert White were set up, they were importing field cameras, the majority of advertising & Commercial photographers used monorail cameras.
The take-up of LF by amateurs really began with the switch of professionals first to LF Digital backs, and fully Digital systems (often monorail). In the late 1990s amateurs began entering the LF market, and by around 2000 there was a glut of LF equipment in the secondhand market, particularly on eBay.
This was a time when analogue equipment prices/values reached an all-time low, the bottom had dropped out of the market for Leica & Rolleiflex, and other high-end MF as well as LF cameras, bargains could be found easily. This was I'd guess around 2002-2008.
I'd bought my first 10x8 from the US and was watching eBay for a decent priced 10x8 enlarger (2004), typically there would be 50 to 60 De Vere 504 enlargers listed and 1 or 2 De Vere 5108 enlargers (UK only). That's the time of a major shift to LF by some amateur photographers, by 2008 as availability dropped prices were rising. I know by 2010 the market had bounced back, I'd had my Leica and Rolleiflex cameras valued, and they matched actual completed sales.
Since then, there has been a steady growth in amateur LF use.
Ian