Archivists hate dry mounting. I know a museum archivist who literally shudders at the thought of dry mounting.
Sandwiching between two pieces of archival matte board or mounting on photo corners are the two best methods I can think of which wouldn't cause Anita, the archivist, to have a fit.
It's not for presentation but she would probably recommend storing photos flat in an archival box with pieces of glassine or archival polyester between.
If you absolutely had to mount a photo to a matte board I would guess that archival wheat starch paste would be the thing to use because, if you had to, you could use steam to remove it from the backing. However, the problem I think you'll find is that, in any kind of fixed mounting, the photo emulsion, the base paper and the backing board will all absorb and release moisture at different rates which will cause the photo to try and crinkle and curl. Since the photo can't move when it's fixed to its backing board, it will eventually self-destruct.
I have photos that I made in photography class 20+ years ago that were carefully dry mounted on matte board. When they were first made, they looked nice but, now that they have aged, the surface is slightly wavy. To make a photo to keep for a long time, whether it be 50 years or 500, I wouldn't dry mount.
I vote with Chris. Use photo corners and sandwich between two pieces of matte board, the front piece, of course, has a window cut out.
It's easy to do. It doesn't require any special equipment and, done carefully, the photos will last longer than you will.