I have used Polycrilic with a lot of succes, is a water based varnish from Minwax. Comes in gloss or Satin, I like Satin better.
About $8 or so for a quart
I tried on Epson Satin Canvas and on paper, Epson Hot press Bright and Epson Enhanced matte
Some of those prints are almost a year old, no cracking or discoloration or yellowing.
One print in my living room has bben under direct light without glass for months and still looks great.
I mixed 20 or 25% purified water and the rest Polycrilic.
First coat in canvas has to be very light and as few strokes as possible to avoid lifting ink
Doesn't leave any addded texture to the print.
I apply 3 light coats, at least 30 min between coats
Hugo