One of the most asked about and experimented with in the alcohol ink communities is all about sealing tiles and YUPO paper.

Step 1:
 Krylon Kamar for the first coat. I like that it because it does not disturb my signature or the painting.  I usually do two coats. (Even if you decide to try resin use this spray first.)

Step 2:
After Kamar varnish, I now use Rust-Oleum often found at a hardware or automotive store.

Step 3:
Alcohol inks will fade in direct sunlight. I tell customers not to have the tiles displayed in direct sunlight so I usually skip this step. However many artists do include this step to help protect against fading caused by harmful UV light rays. It is also moisture resistant and smudge-proof. link to UV Spray

Another Option:
Art Resin
https://www.artresin.com/
To protect artwork from heat many artists are swearing by using Art Resin. This one is very popular and I just got some. It does look simple to use. They have great videos on how to use it. I just got mine and look forward to trying it out. Here are a few links to some YouTube videos on how to use Art Resin.  (Even if you decide to try resin use one or two coats of Krylon Kamar spray first.)
Video to use on tiles. https://youtu.be/i0JBSxDIUsUL