I think the China/HK routes will be hard to re-instate and unfortunately were only overflow routes for LHR when the times were good.
Relations between China and the UK/USA has deteriorated over the last 12-18 months, and I do not see the high number of Chinese visitors returning for some time to the UK. Foreign relations between China and other countries usually heavily dictates visitor numbers to a country from China, via the propaganda they provide to their citizens.
Chinese students coming to UK universities for studies has been a cash cow for the higher education sector, and the number of students now applying has heavily dropped off, and this will have an impact on the numbers using flights too.
Also with the stricter more authoritarian rule coming into place in Hong Kong, it is likely to have an impact on Brits visiting the city, as it was previously considered ex-British colony with democratic rule, which seems to be disappearing
China Airlines will be an interesting one, if that returns? Despite the name, it actually flies to Taipei in Taiwan which is a fully democratic and highly developed country. (But with a long complicated past that is closely linked to China.) I've used the route several times, on their A350's to Australia and got nothing but praise for the service and experience with them.
The flights have always been 80+% full (but that doesn't mean profitable), and is the only direct link between the UK and Taiwan. However the route was never increased in frequency from when launched, remaining at five return flights a week, which poses a question how successful it was? Unlike where they offered direct daily services to cities like Vienna, Frankfurt and Rome and just before the pandemic the daily route to Amsterdam was upgraded to the 777-300.