There is one way to pay rent which requires no RAM or CPU cycles: write a check, and mail it. In my experience, most payees accept the date a check is mailed as the date of payment. (There may be exceptions to this, and I'm not sure what, if any, protections the law provides, so it may not be a valid fallback.)

In general society needs to maintain these low-tech fallbacks to high-tech "improvements". For example, we should keep taxis (that can be flagged down with your hand, and paid for in cash) and not rely solely on Uber, Lyft, etc. We should keep the ability to order from a human at restaurants. We must resist putting the smartphone into the unreplacable critical path of human life. To do so values technology above the value of human life.