I thought about taking other forms of payment, but anything other than crypto (I know, cringe word) is a total PITA, as far as regulations and processes are concerned. 

Lightning has the lowest barrier to entry. Definitely first choice.
I could see a relay taking eCash, USD or Euro stablecoin, monero or doge, or something, tho. 

 LN has a low barrier to entry technically, but higher for the end user, at least psychologically.

Maybe apps like Venmo or CashApp that can deal in crypto can help bridge the gap, but if Bitcoin holdings are non-optional for gaining access to Nostr networks, that will deter many who would otherwise be interested. 

 CashApp and Strike, I guess. Natural partners. 

 PayPal doesn't have LN, does it? 

 no, i think out of the big ones binance and coinbase now finally do

kraken has had it for a long time 

 Don't have to hold Bitcoin, to pay in Bitcoin. You can just throughput your other money at point of sale, same way I use my euro account to pay people in dollars.

I feel like, someone not up to that isn't emotionally ready for Nostr, anyway. 

 they are probably the first but xapo has lightning, on chain, swift, visa and mc payments, their fees are going up in september but i bet there will be competition soon

i'm sure there will be more neobanks adopting LN in the future and then it's all rather moot