@Denny
One of the cool things about Mastodon is the ability to follow hashtags. Just like the one you used for #mastodon, try adding one for #guitar or #customMade or whatever to you posts about those topics. People will see your post if they follow that #. Some people add lots of hashtags to cast a wide net. With no “algorithm” the only way to have content show up in your feed is to follow it and interact with people. And post your YouTube links in your profile. Welcome to the fediverse.