I like commenting on other channels however I won't link unless someone actually asks or on the rare chance there is a question in the comments that my video is on then I do a quick answer and then say if you want to know more I did a video answering more here...

This could be an excellent time to start using the community feature on YouTube and ask your audience some questions...you could be direct or just say I am thinking of "updating" my course (it's here if you haven't seen it) what would you find the most helpful to add? Have some choices for them to choose from...You might not get many or any responses at first however do some other posts and then do another one like this - I have seen this work as I have responded to their requests...You also might consider trying different calls to action in your youtube videos and then looking at the analytics to see if there is drop off when you do the cta...if you haven't done so already start tracking clicks from your videos to see how many are clicking - then looking further to see your website analytics and if those people stay on the landing page or bounce...and yeah of course with the Skool!

Take a look at your analytics to see where most of the views are coming from and go deeper from there...

I have done the 3.5mm input and it works well with this mic (https://www.amazon.com/dp/B0995SY1FL) I have also used this mic (https://www.amazon.com/Blue-Snowball-Microphone-Textured-White/dp/B000EOPQ7E/) as well as the larger yeti. I like the shotgun mics, the sound seems better than with the yeti...however if you are looking to keep doing voice overs or expand out into podcasting then get a Shure mic (https://www.amazon.com/Shure-MV7X-Podcast-Microphone-Voice-Isolating/dp/B09BZZCGC8) You could get the usb however if you are thinking longer term, nailing the voice is such a great way to stand out so the XLR setup is worth it...I like being outside to record and walk so currently using and loving the DJI Mic 2 - it has 32 bit float which means more data for the audio and not the same peaking issues than with 24 bit, it's wireless and noise cancelling - plus can record a backup recording - in case something happens with the wireless...you can get just the transmitter by itself however something really stupid - you can't change the audio bit rate unless you have a receiver or a camera that works with it - such as the DJI action 5 pro (great btw, even has a D Log M setting so can do luts). What I have found after many different mics - it's easy to get way more into it than most of your viewers. :-)

I also started a new channel and am often drawn back to my old one just because it's a lot of content, energy, and I see where I might be able to post to both with the same content and some tweeks...dangerous for sure however there is an overlap between the two...so it's hard to suggest this idea without some more testing and experience to back it up however you might consider where there is overlap...you could then learn from the sponsorship while still feeding your passion...what's most important is alignment with the sponsor which it sounds like you have...it's then a matter of creative genius to see a window of yes on your old channel to maybe having alignment with them on your new? You said totally unrelated however there may be some overlap you have yet to discover...otherwise it may be that you still post to the old channel just less? If that's a yes then it's more likely the brand deal could be more than you might have initially thought...