Tubeless with sealant sounds good on paper...

When you get back, you should get to the bottom of this, to have any reliability. Doesn't sound like a hole in the tire, so must be at the tire beads, or rim tape, or valve. Submerged wheel and tire section in water in basin should show a valve leak, or bead leak. Rim tape, I guess would show a leak through the spoke holes, but with a double-wall rim, that leak could go to ALL spoke holes, so you don't know exactly where, only that it's the rim tape and you need better stuff.