There's been a general increase in online support for bereavement over the last few years, but of course Covid seems to have accelerated it. Listed below are some great groups that I have come across and can recommend.
Let's Talk about Loss - regular online meetups for younger adults
Man2Man - a phone based peer support line for men.
The Grief Network - London based and aimed at younger adults as well.
Suicide & Co - launching soon to provide grants for counselling. In the meantime they have signposting.
The Dinner Party - US based, but also active in the UK. Regular online meetups (normally in person at someone's house).
Widowed and Young - membership gives you access to online groups and is aimed at anyone whose lost a partner under 50.
Black Minds Matter - starting up currently but doing something so needed.
Good Grief Trust has lots of signposting for other charities that can offer advice and support.
There's also the larger and well known charities such as Cruse Bereavement Care, Sue Ryder, Mind that all cover bereavement as part of their service or can signpost.