These seem to be the main relevant insights from the "Adults' Media Lives" report [0] (and they are backed with some good quotes from the participants):

> Participants claimed to be streaming more and viewing less linear TV. This is part of a medium-term trend we have seen over recent years. Participants also reported more of their viewing as being on their own, with less shared/communal viewing overall.Many participants claimed to be viewing more YouTube, in particular, in the past year. For some men, YouTube is now their main (or only) form of viewing.

- p 20.

> Whilst in previous years YouTube was predominantly being used to access specialist content around users' personal interests, it now also seems to serve a broader range of viewing needs. These include “background” viewing (sometimes as a replacement for daytime TV) and videos about random, eclectic, interesting topics – serendipitous content discoveries traditionally associated with linear TV channels.

- p 21.

[0] https://www.ofcom.org.uk/siteassets/resources/documents/rese...