it would help to know jurisdiction/market area because that really affects the options, especially because that’s a rapidly changing landscape right now. some places, prepaid SIMs + cash work well enough, other places it’s better to go with giftcards or prepaid debit cards etc. yet other places there’s definitely no good options to do it. it takes a lot of effort, and you have to remember that you need to consider that any app or service you log into on that phone may end up identifying you against the SIM card, so you need to be really careful in your usage! i hope you find an option that works! :)