Having spent hours trying different Adobe Bridge alternatives: e.g. ...Eagle, Pixave - now vaporware, Neofinder ($40)- very close, but, oddly, doesn't auto-update catalogs, though w/more expensive 'Business' version ($150 for 2 seats), one can set to update on schedule (by days or weeks;-)
The clear 'hands down' winner is.....: (drumroll)...... (cymbal splash)......::::::::
XnView (Mac, Windows, Linux)
As 'cadudesun' says above,
PC users: "For showing/previewing Affinity files the option "Show all graphic formats" should be checked (Tools → Settings... → General)
Mac users: "For showing/previewing Affinity files the option "Show all graphic formats" should be checked (XnView Preferences → General)
PS. Also shows Affinity Publisher files. :))
PPS. It's FREEWARE - be sure to donate if you can.
PPPS. Like all of us here.....: can't wait to see the Affinity Bridge!!!!