Since I use my phone to pay for things, book rides between places and basically existing in general I also keep a power bank on my person and a spare phone in my house
But if I'm not confident on availability I also keep alternatives, I've not used physical money in months (Other than local bus fares), but I do keep some cash on my person, as well as the physical cards that I use virtually on my phone and copies of boarding passes when necessary, not that I've needed any of them recently, I just like covering my bases, it's not a binary situation, I'd also like to keep spares if my only copy was physical
I generally just get the mobile pass and put it in Google Wallet. If I ever run into a situation where my phone is lost/broken/battery-drained, I'll just go up to the check-in desk or a kiosk and get my boarding pass printed. No big deal.