Would you be interested in a virtual internship? https://www.brightnetwork.co.uk/internship-experience-uk/internship-experience-uk-on-demand-schools is for school leavers and there's a policy/charity strand that could be useful if you're thinking of working in the heritage sector. But any of them could be interesting
There are some online volunteering opportunities although I haven't looked to see what's around now. https://doit.life/ could be worth checking.
General useful courses: anything that gets you on good terms with Excel. Lots of online courses and it's really hugely useful in so many jobs and leads of people say they wish they'd got to grips with it earlier. Although I appreciate not hugely related to your actual studies!
You could also surf through Coursera/future learn/open university for anything that captures your interest- sorry that's a bit vague but it's never a bad thing to have things you're passionate about and took time to develop beyond your studies. Looking forward, for work in heritage you might want to look out for things on community engagement or fundraising, I just found this one that could be worth a look https://www.coursera.org/learn/arts-heritage?
Look into some societies at your university and read up on them if you want to start a new hobby or sport- uni is a great time to do that and a good way to meet people
I agree with other people, take time to chill out if you need to but I know a lot of us have had more than enough 'free time' this last year and if your exams have been interrupted you might be keen to do something more focused. Good luck