Hello. I'm Ali, and I'm new in this forum. Actually, I've just registered to write this letter to devs. I really can feel the deep love and care Ubuntu Mate developers put in their distribution. I sincerely wanted to thank you for your time and effort put into this OS. I can see that you've covered a lot more than most distributions do these days. I like accent color and desktop layout settings the most. Unlike some distributions who can't even set the themes that come in their official ISO not to break any colors making the texts on the panel the same color with the panel itself, rendering them completely unreadable (AHEM! Manjaro...) you've obviously done your homework before building this ISO. I really appreciate the wholeness of your OS. So thank you.
As for the complaint, installation gave me an error saying: "Installed shim-signed package post-installiation script subprocess returned error exit status 1"
I don't know what a "shim-signed package" is, but I feel it's important to notify you since it seems to be a problem in a lot of Ubuntu ISOs. After the error, it works out fine. I'm not sure if it causes any problems, but the OS works fine on my computer. I'm looking forward seeing your next release. Keep up the great work!