I mean it depends on where you live. But sports clubs are easy enough to find if you just search for your sport and area.
Same I would guess with other hobbies.
Fitness groups no idea to be honest.
Volunteering: there are usually quite a few forums and such discussing volunteering opportunities. In my country the biggest ones are the volunteer fire department, volunteer first aid (red cross, Johanniter, ASB, Malteser, etc.), technical relief (THW), and different organisations regarding the homeless and poor (biggest ones probably are the Bahnhofsmission and Tafeln) - this is all Germany specific but I’m sure there are somewhat similar things in other countries, too. For smaller things the are often even websites from the local government where you can search for volunteering opportunities interesting you, by topic.
I like to just to Geocaching. There are often a lot of caches in the cities, and a lot of then often have really niche information on I teresting topics. Plus when doing earth or virtual caches, you often need to explore quite a bit.
Saitenbacher Bergsteiger Müsli, Bergsteiger Müsli von saitenbacher!
No but in all seriousness, if I had to choose only one type of cereal, it would be self-made cereal from oats, some nuts and seeds, a bit of fresh fruits (preferably apples and banana) and a mix of (vegan) milk and Joghurt.
I mean it depends on where you live. But sports clubs are easy enough to find if you just search for your sport and area.
Same I would guess with other hobbies.
Fitness groups no idea to be honest.
Volunteering: there are usually quite a few forums and such discussing volunteering opportunities. In my country the biggest ones are the volunteer fire department, volunteer first aid (red cross, Johanniter, ASB, Malteser, etc.), technical relief (THW), and different organisations regarding the homeless and poor (biggest ones probably are the Bahnhofsmission and Tafeln) - this is all Germany specific but I’m sure there are somewhat similar things in other countries, too. For smaller things the are often even websites from the local government where you can search for volunteering opportunities interesting you, by topic.