Having previously posted about some online seminar series of interest to nuclear physicists, I have since come across the site https://researchseminars.org/, which contains a big list of research seminars that can be watched live online. They are hosted by institutes around the world, so you can almost keep watching them 24h a day. I see that the nuclear reaction seminar series are included there already. There is a lot of maths and quite a bit of physics, as well as a smaller selection of computer science and biology (at least as I type this post. Hopefully it will become more inclusive as time goes on). There's a search and filtering facility, or you can just browse and try something that sounds interesting. Big mapping class groups fail the Tits alternative, for example.
Not on the list are the UK nuclear physics lockdown seminars, which are perhaps not supposed to be opened to the world community. I enjoyed hearing about an ex-Surrey undergraduate student's PhD work yesterday when he gave a seminar. Here's a picture of the seminar just getting ready to start.