Anecdotal and only covering a very small part of GTR's network, but my observations would be:
- Weekends are entirely back to normal on the London-Cambridge-Ely-Kings Lynn trains.
- My 'usual' morning late-commute train is probably seeing a similar number of passengers getting on at Ely as 2019, maybe a bit less. It's a little hard to tell as it is 8 carriages (up from 4) and starts from Ely rather than back at Kings Lynn.
- The 1739 Kings Cross-Kings Lynn usually looks rather cosy at 8 carriages now. It probably needs to go back to being 12 as far as Cambridge. Between Cambridge and Ely it probably has similar loads to 2019 (though also not 100% easy to tell - it used to split at Cambridge into an incredibly busy 4-car for Kings Lynn and an almost empty 8 car that terminated at Ely, but the overall numbers do appear similar).
- Cambridge North is seeing a *lot* more passengers board southbound/alight northbound than pre-2020, both on weekdays and weekends. It appears to have really taken off for leisure travellers, rather more so than commuters.
On an average week I'd have made 5 commuting round trips Ely-Cambridge and 1 leisure round trip Ely-London. Now it is probably 3 and 1, so 67% in terms of journeys made.