THis is going to be more audio-visual than I think you intended, but most of my studying for these periods is books, not websites, so its going to be a bit thinner (if you want ww1 book recommendations, let me know and Ill bury you
). Im going to focus on things produced by semi or professional historians for the most part.
For WW1 history, the Western Front Association has an absolute wealth of articles, magazines (subscriber only I think), podcasts and professional historians doing presentations (which get shared on youtube).
Mostly but not entirely Commonwealth focused. Topics range from very approachable to pretty in-depth.
WW1 is a fantastic period to study and this is an amazing resource.
The World War One Historical Association in the US also shares presentations on their youtube and has a number of resources on their site, mostly US focused. The National WW1 Museum in the US also has presentations on their youtube channel.
"Pete & Garys military history" is a podcast that covers a range of topics, with a focus on the two world wars and Britain in particular. Peter Hart is a professional historian and excellent writer. Do note the podcast is probably 75% history and 25% two friends taking the piss out of each other. It is /very/ English.
For WW2 there is Tank Archives, who delves into mostly soviet documents about ww2 era tank production and design. He has a youtube channel as well as a website and has published a couple of books.
On youtube run over to WW2TV. The guests are often professional historians and they get an hour to delve into topics of their interest. Sometimes this is very broad like "logistics in the Battle of the Bulge". Sometimes it is a guy who has researched a particular battalion on 2 days in the battle of Crete. On the channel on Youtube, you have to click the Live tab, since they are not prerecorded.
There is a WW1 counterpart but they had to take a break to sort out a new host, though it was shaping up to be just as good.
In the podcast world, Tom Holland (WW2 historian focusing on the Western powers) has a podcast called "We have ways of making you talk", where he discusses various topics. If you have read books about WW2 theres a fair chance you've already read Holland.
"The Napoleonic quarterly" is an outstanding podcast which invites on established historians in the Napoleonic era to discuss all manner of subjects while following the Napoleonic era in a chronological sense.
There is a bunch of stuff out there that is "guy read a lot of books and now tells you about it" history (which includes my own substack). That stuff is all pretty good (usually...) but its easier to get recommendations for that so the above is more "serious" stuff. Hope it helps.