Slightly tangential but is there a way to download a PWA permanently on a mobile device and have it remain indefinitely even if the upstream site goes offline o

Slightly tangential but is there a way to download a PWA permanently on a mobile device and have it remain indefinitely even if the upstream site goes offline or changes? Every time I try to load a PWA on my phone from my dev laptop, it breaks after a few weeks (days?) for no obvious reason. I investigated this for a bit but eventually gave up and went the electron/wrapper app route. If we can find a real fix for this stupid issue, I would be more than happy to focus on PWAs.