Because of Apple's introduction of the SIP, and the challenges this have posed for the development and the installation process etc, I'm assuming that TotalSpaces is now a niche product.
If TotalSpaces is a niche product, and especially with the low $12 price point, then there's an increased risk that the continued development may not be worth it at some point in the future. So for those of us who are totally dependent on TotalSpaces, it's important that you are financially motivated to continue the development.
For me personally, TotalSpaces is worth infinitely more than $12. But I also realize that $12 is a great price point if you want to attract new users. So I have a suggestion. Why not add a donation option when you check out from your store? That way, people could pay the $12 and then add more if they wanted to. I think a lot of your old users, like me, who are extremely grateful that you are keeping TotalSpaces alive, would be happy to do so.
I also realize that it's probably hard to improve on a software like this, and to be able to add new features that would warrant a paid upgrade on a regular schedule. It's probably more about maintenance and keeping TotalSpaces compatible with future versions of MacOS. So I can see that it may be hard to get more money from your current user base the regular way. If this is the case, a suggestion would be to offer a voluntary yearly subscription, for example. I would gladly sign up to pay $25 per year to assure the continued use and development of TotalSpaces.
You could also probably benefit from have a donation button prominently displayed on your home page. That way, if you don't implement a subscription model etc, current users who are appreciative could still show their support. I would easily donate $50 today if I only knew how!
Anyway, I sincerely want to thank you for continuing the development of TotalSpaces, even in the light of the current SIP reality. TotalSpaces really makes my workflow so much better and more efficient, and I almost couldn't use a Mac without it. And what a great bonus (and a huge selling point for me) to be able to turn off those distracting animations that appear when you switch spaces!