Eurostar say leisure travel is back to 100% of pre-pandemic levels & business travel 80-85%. But due to Brexit they can only provide 70% of pre-pandemic capacity. They've plans to resolve this including trialling online check-in, I've added a summary at https://www.seat61.com/news.htm
The Man in Seat 61:  What's new on the site

News page on the Man in Seat 61 website

@seatsixtyone the 70% occupancy figure doesn’t reflect my recent experience, with apparently full trains (and no delays at St Pancras or Brussels
@mikecrossland . 70% capacity. Peak trains with limited seats sold. Fewer trains so some go out full. Overall, 70% less seats to sell than 2019.